util: remove unused ctxmanager
This was meant as a substitute for Python's "with" with multiple
context managers before we moved to Python 2.7. We're now on 2.7, so
we should have no reason to keep ctxmanager. "hg grep --all
ctxmanager" says that it was never used anyway.
Differential Revision: https://phab.mercurial-scm.org/D73
test-ancestor.py
test-backwards-remove.t
test-branch-tag-confict.t
test-casecollision.t
test-check-commit.t
test-check-execute.t
test-check-pyflakes.t
test-check-pylint.t
test-check-shbang.t
test-contrib-check-code.t
test-contrib-check-commit.t
test-diff-issue2761.t
test-diff-newlines.t
test-diff-reverse.t
test-diff-subdir.t
test-dirstate-nonnormalset.t
test-doctest.py
test-empty-dir.t
test-excessive-merge.t
test-issue1089.t
test-issue1993.t
test-issue842.t
test-locate.t
test-lrucachedict.py
test-manifest.py
test-merge-default.t
test-merge-subrepos.t
test-merge2.t
test-merge5.t
test-revlog-packentry.t
test-run-tests.py
test-unified-test.t
test-update-reverse.t
test-xdg.t