Remove workaround for GRADLE-1079

Previously, `gradle eclipse` would generate .classpath files with
GRADLE_CACHE references.  Now it generates fully-qualified paths to
the user's home directory by default.  This means we can remove the
    eclipseClasspath.variables = [:]
workaround.

build.gradle

@@ -147,9 +147,6 @@ configure(javaprojects) {
     xLintArg = '-Xlint:all'
     [compileJava, compileTestJava]*.options*.compilerArgs = [xLintArg]
 
-    // generate .classpath files without GRADLE_CACHE variable (GRADLE-1079)
-    eclipseClasspath.variables = [:]
-
     // Tie pom generation into the standard build lifecycle (INT-1609)
     assemble.dependsOn generatePom