docs: change `troubles` references to `instability`
Per https://www.mercurial-scm.org/wiki/CEDVocabulary. There are a couple
instances of 'troublesome' which probably need a word, as deriviatives of
'instability' didn't really fit. At least some of these are in the unlinked
obs-terms.rst page.
-------------------------
Evolve Commands Reference
-------------------------
.. highlight:: none
amend
-----
.. hghelp:: amend
evolve
------
.. hghelp:: evolve
fold
----
.. hghelp:: fold
metaedit
--------
.. hghelp:: metaedit
next
----
.. hghelp:: next
obslog
------
.. hghelp:: obslog
pdiff
-----
.. hghelp:: pdiff
previous
--------
.. hghelp:: previous
prune
-----
.. hghelp:: prune
pstatus
-------
.. hghelp:: pstatus
split
-----
.. hghelp:: split
touch
-----
.. hghelp:: touch
uncommit
--------
.. hghelp:: uncommit