Fix confusing macro misuse in GrGLGetGLSLGeneration
Fix confusing macro misuse in GrGLGetGLSLGeneration

The two macros (GR_GL_VER and GR_GLSL_VER) are equivalent, but
everywhere else (including in this function), we're careful to
use them based on the type of version (GL or GLSL). These uses
were inconsistent.

Change-Id: Iefcaf207f29f62541a2fe9252095f6601171a8d5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/558931
Auto-Submit: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Reviewed-by: Jim Van Verth <509afb0bfbb23ecaaf1fb3323209f531b45e75a6@google.com>
Commit-Queue: Jim Van Verth <509afb0bfbb23ecaaf1fb3323209f531b45e75a6@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia