Missing documentation on -funfolding-keeness-factor deprecation

Summary

Location of documentation issue: the GHC user's guide, https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.0

As of v9.0.1, GHC complains:

funfolding-keeness-factor=2.0 is deprecated: -funfolding-keeness-factor is no longer respected as of GHC 8.12

Neither the release notes nor the migration guide currently give any advice on how to replace the flag in user code – they don't even mention the deprecation!

Environment

GHC version used (if appropriate): 9.0.1

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