chore: address issues reported by yarn doctor

[vecerek]

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Description

Addresses all issues uncovered by yarn doctor (yarn dlx @yarnpkg/doctor), specifically:

• undeclared dependencies
• strings referencing the node_modules directory

For more details: https://yarnpkg.com/migration/pnp#calling-the-doctor

Builds on top of #732 and #733 and takes one step closer to the potential adoption of PnP.

Related #735

Type of change

internal change: make all dependencies explicit

Screenshots/Sandbox (if appropriate/relevant):

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How Has This Been Tested?

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• Test A
• Test B

Test Environment:

• OS:
• @graphql-codegen/...:
• NodeJS:

Checklist:

• I have followed the
  CONTRIBUTING doc and the
  style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Further comments

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the solution you did and what alternatives you considered, etc...

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