localrepo: delete obsolete comment about `prefix in repo` raising exception
We dropped support for `prefix in repo`, where `prefix` is a hex
prefix, in
8b86acc7aa64 (context: drop support for looking up context
by ambiguous changeid (API), 2018-04-28), after having deprecated it a
while before that. These days you get a `ProgrammingError` instead if
you pass in a short nodeid.
Differential Revision: https://phab.mercurial-scm.org/D9599
node: import symbols explicitly
There is no point in lazy importing mercurial.node, it is used all over
the place anyway. So consistently import the used symbols directly.
Fix one file using symbols indirectly via mercurial.revlog.
Differential Revision: https://phab.mercurial-scm.org/D9480