gnu: lib2geom: Fix more tests.

gnu: lib2geom: Fix more tests.

There were still two tests failing on aarch64-linux:

1. rotated-rect-test,
2. ellipse-test.

The first one was removed along with the RotatedRect class in latest upstream,
while the second one is yet numerical accuracy related.  It gets fixed by
updating the already existing 'lib2geom-fix-tests' patch.

* gnu/packages/graphics.scm (lib2geom): Bump revision to "2", and update
commit hash to the latest one available.
* gnu/packages/patches/lib2geom-fix-tests.patch: Update patch.