dawn: Remove semicolons.

A cleanup needed for turning on -Wextra-semi in Chromium builds.

Bug: chromium:926235
Change-Id: I3d2b517ad21dfae9e7dc06613a7fe3e98d783b2a
Reviewed-on: https://dawn-review.googlesource.com/c/4841
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/fuzzers/DawnWireServerAndFrontendFuzzer.cpp

@@ -29,7 +29,7 @@ class DevNull : public dawn_wire::CommandSerializer {
     }
     bool Flush() override {
         return true;
-    };
+    }
 
   private:
     std::vector<char> buf;