Remove duplicate source included in jar (#831)

Author: sciencewhiz

vscode-wpilib/resources/gradle/java/build.gradle

@@ -89,7 +89,6 @@ wpi.sim.addDriverstation()
 // knows where to look for our Robot Class.
 jar {
     from { configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) } }
-    from sourceSets.main.allSource
     from('src') { into 'backup/src' }
     from('vendordeps') { into 'backup/vendordeps' }
     from('build.gradle') { into 'backup' }