Added minimum version to DisableExtensions method in chrome_prompt.mojom

Without the minium version flag the Chrome Cleanup Tool will try to use this method even when it's not available on older versions of Chrome.

R=joenotcharles@google.com

Change-Id: I67846a30dca37f66f87a0ac04f1c687c739c4723
Reviewed-on: https://chromium-review.googlesource.com/c/1255571
Commit-Queue: Preston Carpenter <timidger@google.com>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595915}

components/chrome_cleaner/public/interfaces/chrome_prompt.mojom

@@ -65,5 +65,6 @@ interface ChromePrompt {
   //        returned.
   // Returns:
   //  - success: indicates if the extension removal was successful.
-  DisableExtensions(array<ExtensionId> extension_ids) => (bool success);
+  [MinVersion=2] DisableExtensions(array<ExtensionId> extension_ids)
+      => (bool success);
 };