Automated checkin: version bump for firefox 21.0b4 release. DONTBUILD CLOSED TREE a=release

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branch : GECKO210b4_2013042323_RELBRANCH
Added FIREFOX_21_0b4_RELEASE FIREFOX_21_0b4_BUILD1 tag(s) for changeset 04aba2e6927f. DONTBUILD CLOSED TREE a=release

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branch : GECKO210b4_2013042323_RELBRANCH