Conflicting peer dependency for graphql dependency (local development)

When installing for local development, there are warnings about a conflicting peer dependency with `graphql`.

```sh
➜ npm i --cache $(mktemp -d)
npm WARN ERESOLVE overriding peer dependency
npm WARN While resolving: relay-compiler@12.0.0
npm WARN Found: graphql@16.3.0
npm WARN node_modules/graphql
npm WARN dev graphql@"16.3.0" from the root project
npm WARN 50 more (@apollo/client, @apollo/core-schema, ...)
npm WARN
npm WARN Could not resolve dependency:
npm WARN peer graphql@"^15.0.0" from relay-compiler@12.0.0
npm WARN node_modules/@graphql-tools/relay-operation-optimizer/node_modules/relay-compiler
npm WARN relay-compiler@"12.0.0" from @graphql-tools/relay-operation-optimizer@6.4.1
npm WARN node_modules/@graphql-tools/relay-operation-optimizer
npm WARN
npm WARN Conflicting peer dependency: graphql@15.8.0
npm WARN node_modules/graphql
npm WARN peer graphql@"^15.0.0" from relay-compiler@12.0.0
npm WARN node_modules/@graphql-tools/relay-operation-optimizer/node_modules/relay-compiler
npm WARN relay-compiler@"12.0.0" from @graphql-tools/relay-operation-optimizer@6.4.1
npm WARN node_modules/@graphql-tools/relay-operation-optimizer
```

Reproduce the warning with `npm i --cache $(mktemp -d)` and trace the dependency chain from `@graphql-tools/relay-operation-optimizer` to `relay-compiler` and its `graphql` peer requirement. Done means local development installation no longer reports the conflicting peer dependency, while the project's GraphQL dependencies remain compatible.

Written by the indexing model from the issue text.