With the addition of EXT_clip_cull_distance extension
the files are renamed like so -
    ReplaceClipDistanceVariable.h   -> ReplaceClipCullDistanceVariable.h
    ReplaceClipDistanceVariable.cpp -> ReplaceClipCullDistanceVariable.cpp

Bug: angleproject:5458
Change-Id: I277b2d4b6eea6f2014e10acb251284a159292dbc
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2617572
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>