Remove duplicate header wtf/test/string_statics.h from sources list

A header appeared twice in the sources list which confused some
other tool. Seems like better to have it there only once.

Change-Id: If713c5a241fab6e8fb30705240bc534e0598f704
Reviewed-on: https://chromium-review.googlesource.com/c/1290909Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#601331}

third_party/blink/renderer/platform/wtf/BUILD.gn

@@ -167,7 +167,6 @@ jumbo_component("wtf") {
     "text/string_operators.h",
     "text/string_statics.cc",
     "text/string_statics.h",
-    "text/string_statics.h",
     "text/string_to_number.cc",
     "text/string_to_number.h",
     "text/string_utf8_adaptor.h",