Fix end2end tests VertexAttribute* failure
Fix end2end tests VertexAttribute* failure

VertexAttributeTests used 'mediump' precision to sample ushort
with 65533/65534/65535 which exceed the range defined in ESSL Spec.
(Spec "4.5.2 Precision Qualifiers")

Change precision of attribute 'test' and 'expected' to 'highp'
for numbers that exceed the minimum range.

Bug: angleproject:5211
Change-Id: I01e5c999ec43d17a7390835d2ac88ce2bc0b4c5b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2491621
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Reviewed-by: Shahbaz Youssefi <582eeec4f08a2ccd61e3ef52115e6e7c571582de@chromium.org>
Commit-Queue: Shahbaz Youssefi <582eeec4f08a2ccd61e3ef52115e6e7c571582de@chromium.org>

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