Fix a stray quote that snuck into GLSLTest.cpp. This was causing a test failure in TwoElseIfRewriting. BUG=angle:716 Change-Id: I75e21ff586cdef10f0c35985a97fbb7c4783d2fe Reviewed-on: https://chromium-review.googlesource.com/210991 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>