Remove deprecated ChangesList::newFromUser function

newFromUser() is unused in core and all extensions in gerrit,
except BlueSpiceExtensions RSSStandards. (there is a
patch for that I1455052)

Change-Id: I4559146cc0e9973e6e4f6297138cbfd8e387e8b7
Merge "Remove deprecated ChangesList::newFromUser function"