src/dispatch_common.c: Remove Unneeded PUBLIC Annotation

Don't mark epoxy_conservative_gl_version() for export, as it is meant
to be a private API to be used within libepoxy only.

Reviewed-by: Eric Anholt <eric@anholt.net>

src/dispatch_common.c

@@ -315,7 +315,7 @@ epoxy_gl_version(void)
     return epoxy_internal_gl_version(0);
 }
 
-PUBLIC int
+int
 epoxy_conservative_gl_version(void)
 {
     if (api.begin_count)