Fix a typo in the GL_NUM_REQUESTABLE_EXTENSIONS_ANGLE enum value. GL_NUM_REQUESTABLE_EXTENSIONS_ANGLE had a typo between the spec and the header but any user who used our header would still get the correct beaviour. BUG=angleproject:3861 Change-Id: Ibc85607ad41a8419246e057065ab4ce797f0ce66 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1772376 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>