Revert "Fixed typo in closure compiler dependency"

This reverts commit 3e1fffe8b7cca20222a3316d3d0c05c5fd1e955f.

Revert "Use Java 6 compatible version of Closure Compiler"

This reverts commit 86a377390629ddf25aa3387812f1aa03933bc8a8.

The Closure Compiler in gwt-tools is now Java 6 compatible

Change-Id: I4c287dff40fba11dac044a95a93ecef32e287ec8