Remove headers in mojo and data_decoder sources list

Some headers appeared twice in some sources list. This confused
some other tools so it seems like a good idea
to only have them there once.

Change-Id: Ifa0c7b2e0fbb8b7ec401bad2737384cffa3d940a
Reviewed-on: https://chromium-review.googlesource.com/c/1290949Reviewed-by: Jay Civelli <jcivelli@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#601177}

mojo/public/cpp/bindings/BUILD.gn

@@ -53,7 +53,6 @@ component("bindings_base") {
     "lib/message_internal.h",
     "lib/scoped_interface_endpoint_handle.cc",
     "lib/serialization.h",
-    "lib/serialization.h",
     "lib/serialization_context.cc",
     "lib/serialization_context.h",
     "lib/serialization_forward.h",

services/data_decoder/public/cpp/BUILD.gn

@@ -14,7 +14,6 @@ source_set("cpp") {
     "safe_json_parser.h",
     "safe_json_parser_impl.cc",
     "safe_json_parser_impl.h",
-    "safe_json_parser_impl.h",
     "safe_xml_parser.cc",
     "safe_xml_parser.h",
   ]