The android binary size is increased incorrectly because the autogen
kFunction* variables are detected as mutable constants. Rename them to
function* to workaround this.

Bug: angleproject:3823
Change-Id: Ia335d1ae97ce5276a0ff8b9e432b53181cc36680
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1762494Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>