[gin] Remove V8_USE_PERFETTO definition in gin

Now that v8 declares V8_USE_PERFETTO as an external definition that
appears whenever including the main V8 headers
(https://chromium-review.googlesource.com/c/v8/v8/+/2621083), we can
remove its definition from gin.

Bug: 1006541
Change-Id: I5b48bedfce1588c078fda0c307c0f345dcb222ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2622096
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842468}

gin/BUILD.gn

@@ -75,10 +75,6 @@ component("gin") {
 
   defines = [ "GIN_IMPLEMENTATION" ]
 
-  if (use_perfetto_client_library) {
-    defines += [ "V8_USE_PERFETTO" ]
-  }
-
   public_deps = [
     "//base",
     "//v8",