fix(useIsMutating): use MutationKey instead of QueryKey

[amen-souissi]

Fix TypeScript annotations and update the useIsMutating doc:
use MutationKey instead of QueryKey

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[codecov]

Codecov Report

Merging #3222 (2e696ef) into master (c532d81) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3222   +/-   ##
=======================================
  Coverage   96.47%   96.47%           
=======================================
  Files          45       45           
  Lines        2271     2271           
  Branches      639      639           
=======================================
  Hits         2191     2191           
  Misses         77       77           
  Partials        3        3           

Impacted Files	Coverage Δ
src/react/useIsMutating.ts	100.00% <ø> (ø)

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[tannerlinsley]

🎉 This PR is included in version 3.34.12 🎉

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• npm package (@latest dist-tag)
• GitHub release

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[tannerlinsley]

🎉 This PR is included in version 4.0.0-alpha.9 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

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