cmdutil: remove the redundant commit during amend There was an extra commit made during the amend operation to track the changes to the working copy. However, this logic was written a long time back and newer API's make this extra commit redundant. Therefore, I am removing the extra commit. After this change, I noticed that - Execution time of the cmdutil.amend improved by over 40%. - Execution time of "hg commit --amend" improved by over 20%. Test Plan: I ensured that the all the hg tests passed after the change. I had to fix a few tests which were aware of the extra commit made during the amend. Differential Revision: https://phab.mercurial-scm.org/D636