Change PRESUBMIT warning text for obsolete predeclaration

When a patch removes the code that required a predeclaration the PRESUBMIT would
print a warning with a message like "ResourceRequestInfo forward declaration is
becoming useless". I didn't understand the meaning of the message.

Change the message to "ResourceRequestInfo forward declaration is no longer
needed" which hopefully will be easier to understand.

BUG=662195

Review-Url: https://codereview.chromium.org/2890413002
Cr-Commit-Position: refs/heads/master@{#473169}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index a320354..d9777e0 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -1732,7 +1732,7 @@
         for decl in useless_fwd_decls:
           if input_api.re.search(r'\b%s\b' % decl, line[1:]):
             results.append(output_api.PresubmitPromptWarning(
-              '%s: %s forward declaration is becoming useless' %
+              '%s: %s forward declaration is no longer needed' %
               (f.LocalPath(), decl)))
             useless_fwd_decls.remove(decl)