registry_xml.py was not included in gen_gl_enum_utils.py inputs.
gen_gl_enum_utils might not run when it should because of this missing
dependency.

Discovered in https://chromium-review.googlesource.com/c/angle/angle/+/1838418/6/src/libANGLE/gl_enum_utils_autogen.cpp#1810

Bug: angleproject:4000
Change-Id: Ib98df7046a59800c102be54b44f46a203ba77c42
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1857645
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>