Remove rule prohibiting including src/v8.h

The dust has settled and it can now be used like any other header file

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1605973002

Cr-Commit-Position: refs/heads/master@{#33395}

src/DEPS

@@ -17,13 +17,6 @@ include_rules = [
 ]
 
 specific_include_rules = {
-  ".*\.h": [
-    # Note that src/v8.h by now is a regular header file, it doesn't provide
-    # any special declarations besides the V8 class. There should be no need
-    # for including it in any .h files though. This rule is just a reminder,
-    # and can be removed once the dust has settled.
-    "-src/v8.h",
-  ],
   "d8\.cc": [
     "+include/libplatform/libplatform.h",
   ],