Remove shaders.negative.unused_uniform_precision_matching

Remove shaders.negative.unused_uniform_precision_matching

The GLSL spec was updated to "the types, precisions and any location
specifiers of all statically used uniform variables with the same name
must match across shaders that are linked into a single program."

which makes the unused_uniform_precision_matching test invalid.

Updating this test to use statically used uniforms would be
redundant to used_uniform_precision_matching.

Components: OpenGL
VK-GL-CTS issue: 1249

Affects:
KHR-GLES32.shaders.negative.unused_uniform_precision_matching

Change-Id: I6a60c9355144f1d539a6463d913844129e6dfc8d