dirstate-tracked-key: update the config value to match latest discussion
Special cases are not special enough, we align the option name on the other.
The `version` value is undocumented for now as it can only have a single value.
It is supported in the code to properly detect and abort if more value are
introduced in the future value.
Differential Revision: https://phab.mercurial-scm.org/D12184
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..