Remove the dirty checking of matrix uniform update at frontend and
always let backend update whenever glUniformMatrix* is called. Profiled
with UniformsBenchmark/* with vulkan backend, performance increases
around 6% when data being updated is changing and performance increases
around 2% when data being updated stays same.

Bug: angleproject:3705
Change-Id: I8eaf6a1231e634b69c6dc540db1b9d3a312bf45d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1709725
Commit-Queue: Jiacheng Lu <lujc@google.com>
Reviewed-by: Tobin Ehlis <tobine@google.com>