REGRESSION (r138184): transitions/transitions-parsing.html is failing on GTK

REGRESSION (r138184): transitions/transitions-parsing.html is failing on GTK
https://bugs.webkit.org/show_bug.cgi?id=105522

Reviewed by Xan Lopez.

.:

Remove the configuration flag covering unprefixed CSS transition property names.
It does not introduce any dependency. The unprefixed property names should be
available by default.

* configure.ac:

Source/WebCore:

Remove the feature define overriding for the unprefixed CSS transition property names
define as it is not required.

No new tests - no new functionality.

* GNUmakefile.am:

LayoutTests:

Remove a failure expectation for a test that's now passing.

* platform/gtk/TestExpectations:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@138795 268f45cc-cd09-0410-ab3c-d52691b4dbfc