Array brackets are not included in ShaderVariable::name, so they
don't need to be pruned from there either when using the name to
look up the variable.

BUG=angleproject:2267
TEST=angle_unittests --gtest_filter=*InitOutput*Array*

Change-Id: I2b80a88c1d67f7f0dde12880bcfb35fb6d861cd0
Reviewed-on: https://chromium-review.googlesource.com/909109Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>