[FLINK-11106] Remove Scala nature from flink-yarn module

Since all Scala code has been removed from the flink-yarn module, we can now safely
remove the Scala nature from the flink-yarn module.

flink-yarn/pom.xml

@@ -209,112 +209,6 @@ under the License.
  </executions>
  </plugin>
 
- <!-- Scala Compiler -->
- <plugin>
- <groupId>net.alchim31.maven</groupId>
- <artifactId>scala-maven-plugin</artifactId>
- <executions>
- <!-- Run scala compiler in the process-resources phase, so that dependencies on
- scala classes can be resolved later in the (Java) compile phase -->
- <execution>
- <id>scala-compile-first</id>
- <phase>process-resources</phase>
- <goals>
- <goal>compile</goal>
- </goals>
- </execution>
-
- <!-- Run scala compiler in the process-test-resources phase, so that dependencies on
- scala classes can be resolved later in the (Java) test-compile phase -->
- <execution>
- <id>scala-test-compile</id>
- <phase>process-test-resources</phase>
- <goals>
- <goal>testCompile</goal>
- </goals>
- </execution>
- </executions>
- <configuration>
- <jvmArgs>
- <jvmArg>-Xms128m</jvmArg>
- <jvmArg>-Xmx512m</jvmArg>
- </jvmArgs>
- </configuration>
- </plugin>
-
- <!-- Eclipse Integration -->
- <plugin>
- <groupId>org.apache.maven.plugins</groupId>
- <artifactId>maven-eclipse-plugin</artifactId>
- <version>2.8</version>
- <configuration>
- <downloadSources>true</downloadSources>
- <projectnatures>
- <projectnature>org.scala-ide.sdt.core.scalanature</projectnature>
- <projectnature>org.eclipse.jdt.core.javanature</projectnature>
- </projectnatures>
- <buildcommands>
- <buildcommand>org.scala-ide.sdt.core.scalabuilder</buildcommand>
- </buildcommands>
- <classpathContainers>
- <classpathContainer>org.scala-ide.sdt.launching.SCALA_CONTAINER</classpathContainer>
- <classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER</classpathContainer>
- </classpathContainers>
- <excludes>
- <exclude>org.scala-lang:scala-library</exclude>
- <exclude>org.scala-lang:scala-compiler</exclude>
- </excludes>
- <sourceIncludes>
- <sourceInclude>**/*.scala</sourceInclude>
- <sourceInclude>**/*.java</sourceInclude>
- </sourceIncludes>
- </configuration>
- </plugin>
-
- <!-- Adding scala source directories to build path -->
- <plugin>
- <groupId>org.codehaus.mojo</groupId>
- <artifactId>build-helper-maven-plugin</artifactId>
- <version>1.7</version>
- <executions>
- <!-- Add src/main/scala to eclipse build path -->
- <execution>
- <id>add-source</id>
- <phase>generate-sources</phase>
- <goals>
- <goal>add-source</goal>
- </goals>
- <configuration>
- <sources>
- <source>src/main/scala</source>
- </sources>
- </configuration>
- </execution>
- <!-- Add src/test/scala to eclipse build path -->
- <execution>
- <id>add-test-source</id>
- <phase>generate-test-sources</phase>
- <goals>
- <goal>add-test-source</goal>
- </goals>
- <configuration>
- <sources>
- <source>src/test/scala</source>
- </sources>
- </configuration>
- </execution>
- </executions>
- </plugin>
-
- <!-- Scala Code Style, most of the configuration done via plugin management -->
- <plugin>
- <groupId>org.scalastyle</groupId>
- <artifactId>scalastyle-maven-plugin</artifactId>
- <configuration>
- <configLocation>${project.basedir}/../tools/maven/scalastyle-config.xml</configLocation>
- </configuration>
- </plugin>
-
  <plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-jar-plugin</artifactId>