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}
diff --git a/third_party/blink/renderer/core/BUILD.gn b/third_party/blink/renderer/core/BUILD.gn
index a0359b4..b218114 100644
--- a/third_party/blink/renderer/core/BUILD.gn
+++ b/third_party/blink/renderer/core/BUILD.gn
@@ -1573,11 +1573,10 @@
   ":make_core_generated_css_primitive_value_unit_trie",
   ":make_core_generated_computed_style_initial_values",
   ":make_core_generated_computed_style_base",
-  ":make_core_generated_css_value_id_mappings",
-  ":make_core_generated_css_property_baseclass",
   ":make_core_generated_css_longhand_property_classes",
-  ":make_core_generated_css_shorthand_property_classes",
+  ":make_core_generated_css_property_baseclass",
   ":make_core_generated_css_property_names",
+  ":make_core_generated_css_shorthand_property_classes",
   ":make_core_generated_css_value_id_mappings",
   ":make_core_generated_cssom_types",
   ":make_core_generated_event_factory",