meson: gl: remove non-headers from gl_prototype_headers
This made the meson build install those files, while they aren't
installed with the autotools build.
https://bugzilla.gnome.org/show_bug.cgi?id=796274
diff --git a/gst-libs/gst/gl/meson.build b/gst-libs/gst/gl/meson.build
index 4ab5c57..a483066 100644
--- a/gst-libs/gst/gl/meson.build
+++ b/gst-libs/gst/gl/meson.build
@@ -75,10 +75,8 @@
'glprototypes/gles.h',
'glprototypes/gstgl_compat.h',
'glprototypes/gstgl_gles2compat.h',
- 'glprototypes/Makefile.am',
'glprototypes/opengl.h',
'glprototypes/query.h',
- 'glprototypes/README',
'glprototypes/shaders.h',
'glprototypes/sync.h',
'glprototypes/vao.h',