Use version 3 for DisableExtensions not 2

We already shipped a chrome version with version 2 exposed, so the
Chrome Cleanup Tool will try to use this method when it doesn't exist
unless we bump the minimum version.

Change-Id: I6c0bf1209da85ea54f4e7d2d365d64ac8a98ba66
Bug: 889568
Reviewed-on: https://chromium-review.googlesource.com/1258296
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@{#596254}

components/chrome_cleaner/public/interfaces/chrome_prompt.mojom

@@ -65,6 +65,6 @@ interface ChromePrompt {
   //        returned.
   // Returns:
   //  - success: indicates if the extension removal was successful.
-  [MinVersion=2] DisableExtensions(array<ExtensionId> extension_ids)
+  [MinVersion=3] DisableExtensions(array<ExtensionId> extension_ids)
       => (bool success);
 };