fix(mutate): serialize clientless patches correctly

[rexxars]

This PR fixes an issue where passing a clientless patch (new Patch('doc-id')) will result in the mutation getting incorrectly serialized when passed to mutate().

Actually serialized body:

{mutations: [{id: 'doc-id', set: {foo: 'bar'}]}

Expected body:

{mutations: [{patch: {id: 'doc-id', set: {foo: 'bar'}]}}

[stipsan]

Good catch!!

[github-actions]

🎉 This PR is included in version 5.4.2 🎉

The release is available on:

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

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