[graphiql] remove unused dependencies graphql-language-service and markdown-it

[dimaMachina]

they are used in @graphiql/react but not in graphiql

[changeset-bot]

🦋 Changeset detected

Latest commit: acac8cd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
graphiql	Patch

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[acao]

@dimaMachina the others seem fine, however @graphiql/toolkit is used by graphiql here:

packages/graphiql/src/cdn.ts

i imagine this is why the e2e suite is failing

[dimaMachina]

@acao tests failed due dedup of markdown-it, was fixed by adding overrides in package.json

[webpack-dev-server] ERROR in ../../../node_modules/markdown-it/lib/common/entities.js 6:0-59
Module not found: Error: Package path ./lib/maps/entities.json is not exported from package /Users/dmytro/Desktop/GUILD/graphiql/node_modules/entities (see exports field in /Users/dmytro/Desktop/GUILD/graphiql/node_modules/entities/package.json)