Revert "tf-a-lts2.8-gerrit-tforg-l*: Set TF_GERRIT_REFSPEC to lts-v2.8 branch"

This reverts commit 90ada6da6e36723c6091518a0bbc753f7f10982c.

Reason for revert: This change should have gone to tf-a-lts2.8-tftf-gerrit-tforg-l* jobs.

Change-Id: Ib244df5bf45c941c061b64adc4f17976178a0fbd
2 files changed