Add timvp to opengl/OWNERS

aosp/1623124 recently updated the OWNERS file for GraphicsEnvironment
to point to opengl/OWNERS, rather than listing owners directly. This CL
adds timvp@, since he was listed previously.

Test: build
Change-Id: Ibb375cce8b860c38f61cf563ae632a90101bb0e5
diff --git a/opengl/OWNERS b/opengl/OWNERS
index 8fac0cc..a9bd4bb 100644
--- a/opengl/OWNERS
+++ b/opengl/OWNERS
@@ -3,3 +3,4 @@
 ianelliott@google.com
 jessehall@google.com
 lpy@google.com
+timvp@google.com