remove universe.as_Universe

[orbeckst]

universe.as_Universe is not really needed

mdanalysis/package/MDAnalysis/core/universe.py

Lines 1327 to 1328 in 45e56e8

	# TODO: what is the point of this function???
	def as_Universe(*args, **kwargs):

and can be removed.

EDIT: @IAlibay found in PR #2922 that LeafletFinder is also affected and will not anymore accept a filename as input

• remove for 2.0.0
• deprecate as_Universe in 1.0.1 (see PR Backport 1.0.1 #2798 )
• deprecate filename argument for LeafletFinder in 1.0.1

[IAlibay]

I think the only use case of as_Universe is LeafletFinder, which to be honest is strange behaviour for MDAnalysis as a whole (i.e. we don't usually pass paths to files to analysis classes). Unless there's any objections, I'd suggest just making LeafletFinder's universe argument accept solely Universes.

[orbeckst]

Thanks for looking into what is affected. I added a deprecation note to LeafletFinder to the backport.