python: remove fix-GenericAlias patch

[Grimler91]

It does not seem to be necessary any more, and it causes issues:
#7432

[Grimler91]

@landfillbaby do you remember what the error/issue was when you added the patch? The old CI logs cannot be downloaded anymore

[landfillbaby]

i think i got the patch from this debian bug
and looking at that thread now, the patch i used was wrong to begin with, it should have been _CallableGenericAlias(type(list[int])) rather than _CallableGenericAlias(list[int])
i think the actual underlying problem was building python 3.9 and then testing its stdlib using the host system's 3.8 or 3.7, so this should definitely be merged