Bump transformers package to 0.6.1.0

This continues the saga with Foldable1 in base: transformers-0.6.1.0 now provides instances of Foldable1 to avoid orphans in compatibiltiy packages. It would be nice to update in time for GHC 9.6. CC @phadej @RyanGlScott @RossPaterson

I'd do the bump myself, but AFAIU https://gitlab.haskell.org/ghc/packages/transformers cannot mirror the upstream Darcs repository automatically, so if someone could syncronize them manually?.. @bgamari is it something you can do please?

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