Headers in :make_core_generated_css_value_id_mappings appeared twice

The target :make_core_generated_css_value_id_mappings was listed
twice which made its output be twice in some sources lists. This
confused some tools. Seems better to only have it there once.

R=fs@opera.com

Change-Id: I1da2cfbda7021fa5262d0c0a74b894989fc200de
Reviewed-on: https://chromium-review.googlesource.com/c/1290929
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#601105}
1 file changed