Stop adding -Wextra-semi.

It is already on by default.

TBR=thakis@chromium.org
BUG=chromium:926235

Change-Id: I9488ca58c2fb0d85fd4b0f7325e2749d4570c081
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/53270
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 111c69e..83fc631 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -83,9 +83,6 @@
   defines = []
   if (is_clang) {
     cflags += [ "-Wshadow" ]
-
-    # TODO(thakis): Remove once this is on globally, https://crbug.com/926235
-    cflags += [ "-Wextra-semi" ]
   }
   if (is_linux) {
     if (current_cpu == "x64") {