Fix prefer-flat in GrGLCaps

Another accidental logic change when removing GrGLDriver::kANGLE.

Change-Id: I3b79e86d66ad2edc6801d879ed54f9556aa97aa6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/406940
Commit-Queue: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
1 file changed