copies: no longer change the sidedata flag With the new sidedata storage that include data about all file changes, every revision has one, so the sidedata flag is not longer a good way to spot changeset with copy information. So we drop this check to simplify the code We optimisation itself provided an interesting speedup, so we will likely reintroduce something similar, with a dedicated flag, in the future. Differential Revision: https://phab.mercurial-scm.org/D9116