Fix migration name substitution

[vonforum]

Faulty regex from the beginning of the project (here)

[dolezel]

Thanks for noticing 👍
But regarding it didn't work it is probably useless or maybe it should be [_ ]

[vonforum]

Ah, yes, actually. I was thinking the spaces get replaced in the join call a couple lines above anyway, but if the name is wrapped in quotes, they count as a single argument.