evolve: use repo._bookmarks.recordchange instead of repo._bookmarks.write
We want to get rid of the api repo._bookmarks.write and this
patch removes its use in evolve.py.
Before this patch, we were using repo._bookmarks.write to save bookmarks change
immediately instead of repo._bookmarks.recordchange that write change when
transaction ends.
evolve: indentation change for making next patch more legible
In the next patch: "evolve: use repo._bookmarks.recordchange instead of
repo._bookmarks.write" we need to add a transaction in the rewrite function.
To do so adds an indentation level and makes the patch harder to review.
This patch makes the indentation change so that the next patch is easier to
review.