upgrade maven compiler plugin

[itsankit-google]

Step #4 - "build-cdap": [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.7.0:compile (default-compile) on project wrangler-api: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.7.0:compile failed: 

Plugin org.apache.maven.plugins:maven-compiler-plugin:3.7.0 or one of its dependencies could not be resolved: Failed to collect dependencies at org.apache.maven.plugins:maven-compiler-plugin:jar:3.7.0 -> org.codehaus.plexus:plexus-java:jar:0.9.2: Failed to read artifact descriptor for org.codehaus.plexus:plexus-java:jar:0.9.2: 

Could not transfer artifact org.codehaus.plexus:plexus-java:pom:0.9.2 from/to central (https://repo.maven.apache.org/maven2): transfer failed for https://repo.maven.apache.org/maven2/org/codehaus/plexus/plexus-java/0.9.2/plexus-java-0.9.2.pom: Connection reset -> [Help 1]