Removed unnecessary GL extensions

We've been cargo-culting these extensions around for a long time, but it
appears they aren't actually necessary.

Change-Id: I536ec9b81643c7d35f108d230233bb6990fcb5d7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/441519
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
5 files changed