histedit: use hg.updaterepo() to avoid ui.{push|pop}buffer() hack
In some parts of code, we call hg.update() and surround that with
ui.pushbuffer() and ui.popbuffer() to suppress the output returned by
hg.update().
We have hg.updaterepo() which does not writes to UI and can be used instead.
Differential Revision: https://phab.mercurial-scm.org/D3862
public attribute not declared in interfaces: badpeer.badattribute
public attribute not declared in interfaces: badpeer.badmethod