Remove java_library2()

In [1] provided_deps parameter was added to java_library() rule making
our custom java_library2() unnecessary. This upstream change addresses
github issue #68 [2].

[1] https://github.com/facebook/buck/commit/cea4e34466af532744c5c1ead9f48780c128f047
[2] https://github.com/facebook/buck/pull/68

Change-Id: I51c5385ba3e4c73f209ed9213272377d53806e22