docs: fix `integration-with-bun.mdx` TypeScript issue

[yamcodes]

Fix a TypeScript issue resulting from a breaking change in Bun or GraphQL Yoga. (Unforuntately, it seems somebody didn't play nice with SemVer conventions)

The error occurs with the following versions:

• [email protected]
• [email protected]

The error as well as discussions about solutions are detailed here:

• https://github.com/dotansimha/graphql-yoga/issues/3003#issuecomment-2255533003
• https://github.com/dotansimha/graphql-yoga/discussions/2644#discussioncomment-10273630
• https://github.com/dotansimha/graphql-yoga/discussions/2644#discussioncomment-10360551

This PR uses the discussed solution to fix the error.