Don't use too many color attachments in clear test
Don't use too many color attachments in clear test

GL_MAX_COLOR_ATTACHMENTS has a minimum value of 4.  The test was
unconditionally using 5 attachments.

Bug: angleproject:4172
Change-Id: I793c297b50e3fdc54f75e2c5608508279028359f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1937808
Commit-Queue: Shahbaz Youssefi <582eeec4f08a2ccd61e3ef52115e6e7c571582de@chromium.org>
Reviewed-by: Jonah Ryan-Davis <682bdb9e7d8ba359ef169b8db374e7a99d394a46@google.com>

ppy/angle,ppy/angle,ppy/angle,ppy/angle