message: Fix extra semicolon in DAWN_UNUSED_FUNC
  This is fixes the soon to be added -Wc++98-compat-extra-semi wraning.
  TBR=kainino@chromium.org
diff: @@ -85,7 +85,7 @@ extern void __cdecl __debugbreak(void);
  // It seems that (void) EXPR works on all compilers to silence the unused variable warning.
  #define DAWN_UNUSED(EXPR) (void)EXPR
  // Likewise using static asserting on sizeof(&FUNC) seems to make it tagged as used
  -#define DAWN_UNUSED_FUNC(FUNC) static_assert(sizeof(&FUNC) == sizeof(void (*)()), "");
  +#define DAWN_UNUSED_FUNC(FUNC) static_assert(sizeof(&FUNC) == sizeof(void (*)()), "")
  // Add noop replacements for macros for features that aren't supported by the compiler.
  #if !defined(DAWN_LIKELY)
  