push heroku masterでのMojoExecutionException

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>任意</groupId>
  <artifactId>任意</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
      <!-- 文字コードの設定 -->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>
    <!--javaxを読込む—>
  <dependencies>
      <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.0.1</version>
        <scope>provided</scope>
      </dependency>
      <dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <version>1.4.200 </version>
</dependency>
  </dependencies>


  <build>
    <sourceDirectory>src</sourceDirectory>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <release>11</release>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-war-plugin</artifactId>
        <version>3.2.3</version>
        <configuration>
          <warSourceDirectory>WebContent</warSourceDirectory>
        </configuration>
      </plugin>
      <!-- Herokuから取ってきたwebappのプラグイン -->
     <!--  https://devcenter.heroku.com/ja/articles/java-webapp-runner -->
       <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals><goal>copy</goal></goals>
                    <configuration>
                        <artifactItems>
                            <artifactItem>
                                <groupId>com.heroku</groupId>
                                <artifactId>webapp-runner</artifactId>
                                <version>9.0.30.0</version>
                                <destFileName>webapp-runner.jar</destFileName>
                            </artifactItem>
                        </artifactItems>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
  </build>
</project>

heroku create

git push heroku master

[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

remote:        [INFO] Changes detected - recompiling the module!
remote:        [INFO] Compiling 9 source files to /tmp/build_7bd808c5/target/classes
remote:        [INFO] ------------------------------------------------------------------------
remote:        [INFO] BUILD FAILURE
remote:        [INFO] ------------------------------------------------------------------------
remote:        [INFO] Total time:  8.485 s
remote:        [INFO] Finished at: 2021-02-27T09:23:08Z
remote:        [INFO] ------------------------------------------------------------------------
remote:        [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project whisper: Fatal error compiling: invalid flag: --release -> [Help 1]
remote:        [ERROR] 
remote:        [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
remote:        [ERROR] Re-run Maven using the -X switch to enable full debug logging.
remote:        [ERROR] 
remote:        [ERROR] For more information about the errors and possible solutions, please read the following articles:
remote:        [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
remote: 
remote:  !     ERROR: Failed to build app with Maven
remote:        We're sorry this build is failing! If you can't find the issue in application code,
remote:        please submit a ticket so we can help: https://help.heroku.com/
remote: 
remote:  !     Push rejected, failed to compile Java app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !   Push rejected to へロクにcreateしたアプリ名.
remote: