Remove unnecessary ide.gradle file and remove 'apply from: IDE_GRADLE' plugin declarations from Gradle module build files.

All IDE configuration logic is handle by the Spring Build Conventions Gradle project.

gradle/ide.gradle

@@ -1,6 +0,0 @@
-idea {
-	module {
-		testSourceDirs += file('src/integration-test/java')
-	}
-}
-