Fix non-terminating regexp in roundtrip-test.js from 553d6a4c

* Commit 553d6a4c fixed normalization by introducing this
  regexp snippet: (?: [^>]+)*

* This particular pattern (..+)* has been responsible for several
  instances of non-terminating regexps in Parsoid.  See fixes made
  in the following commits.
  * Commit 9d53f31b
  * Commit 76e57710
  * Commit b6a6b1f7

  During development, we also ran into this pattern couple other
  times which didn't make it into comitted code but was discussed
  on IRC.

* We should be careful when reviewing regexps to catch this pattern
  before it becomes a problem.

* With this fix, "node roundtrip-test.js --prefix ru City_and_Colour"
  runs to completion.

Change-Id: Ic6ab8ddeb6aaec7fcb36488163a129519cda2376