chore: update filename for 0.22.1 migration notes

[ericswanson-dfinity]

Description

dfx 0.22.1 has migration notes, even though the changes are not breaking.

How Has This Been Tested?

Just updates docs

Checklist:

• [x] The title of this PR complies with Conventional Commits.
• [ ] I have edited the CHANGELOG accordingly.
• [ ] I have made corresponding changes to the documentation.

[ericswanson-dfinity]

Looks like we are going with 0.23.0 after all