GrGLExtensions: remove unneded unique_ptr

Change-Id: Ic949b186fbb4f503d2edbea7033ad242c12ad101
Reviewed-on: https://skia-review.googlesource.com/115640
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
2 files changed