I'm not so sure, graphql is not imported or directly used anywhere in this codebase.

What specific problem would this PR alleviate? I'm not familiar what it has to do with Yarn berry.

PnP strict mode (default one) of yarn berry is now following this rule:

PnP operating under strict mode will prevent packages to require dependencies that they don't explicitly list (even if one of their others dependencies happens to depend on it)
(https://yarnpkg.com/features/pnp)

This mean that as this package is using apollo-link which has graphql as a peer dependencies yarn will show the following errors:

➤ YN0002: │ apollo-upload-client@npm:13.0.0 doesn't provide graphql@^0.11.3 || ^0.12.3 || ^0.13.0 || ^14.0.0 || ^15.0.0 requested by apollo-link@npm:1.2.14
➤ YN0002: │ apollo-upload-client@npm:13.0.0 doesn't provide graphql@^0.11.0 || ^0.12.0 || ^0.13.0 || ^14.0.0 || ^15.0.0 requested by apollo-link-http-common@npm:0.2.16

Obviously yarn offers a way to fix this locally with packageExtensions but it's better if it's directly in the package.json of the library.

I came across this article if you want more informations: https://dev.to/arcanis/implicit-transitive-peer-dependencies-ed0