histedit: removing the experimental config 'histeditng' This config has been around for about 2 years now. So, it can be assumed to be stable. Therefore, I am removing the config. This also makes the test 'test-histedit-base.t' compatible with chg. Test Plan: - Ran the test 'test-histedit-base.t' with and without '--chg' option. - Ran all the other tests without '--chg' option. - Checked the output of 'hg help histedit'. Differential Revision: https://phab.mercurial-scm.org/D942

  $ rm -rf a
  $ hg init a
  $ cd a
  $ echo a > a
  $ hg ci -Am0
  adding a
  $ hg tag t1 # 1
  $ hg tag --remove t1 # 2

  $ hg co 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg tag -f -r0 t1
  $ hg tags
  tip                                3:a49829c4fc11
  t1                                 0:f7b1eb17ad24

  $ cd ..