scippneutron needs mantid for building docs and tests

[MridulS]

The logic should be moved to the template here so copier update doesn't mess up scippneutron downstream

[YooSunYoung]

I thought it'll create a conflict when the related part is updated from the copier,
if a file is updated after copier-(copy/update).
We should just check the diff file by file after copier update, before we commit the changes...?

I think we don't want to include every cases in the copier-template
and using mantid in the scippneutron is one of the special cases, no...?

[SimonHeybrock]

Agree with @YooSunYoung. As far as I have seen conflicts usually happen only "once", and if they are resolved correctly then subsequent updates (that do not further change the specific code location) work as intended.