ci: run the gql tests on gql backend changes

Created by: jhchabran

As @Strum355 pointed out on Slack it's logical to expect the backend integration tests to be run when changing the backend integration tests in a PR.

TODO:

• Drop the test commit to trigger the changes
• Regenerate the CI inline docs.

Test plan

New plan:

~/work/sourcegraph U ci/run-backend-integrations-test-on-graphqlbackend $ sg ci preview
If the current branch were to be pushed, the following pipeline would be run:


  • Detected run type: Pull request
  • Detected diffs: Go, GraphQL
  • Computed build steps:
    • Integration tests
      • :docker: 🚧 Build server
      • ⛓️ Backend integration tests → depends on server:candidate
      • :docker:🧠 Code Intel QA → depends on server:candidate
    • Linters and static analysis
      • 💄 Prettier
      • 📋 Misc linters
      • 💄 :graphql: GraphQL lint
    • Client checks
      • :puppeteer:🔌 Puppeteer tests prep
      • :puppeteer:🔌 Puppeteer tests chunk #1 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #2 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #3 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #4 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #5 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #6 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #7 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #8 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests chunk #9 → depends on puppeteer:prep
      • :puppeteer:🔌 Puppeteer tests finalize → depends on puppeteer:chunk:1, puppeteer:chunk:2, puppeteer:chunk:3,
      puppeteer:chunk:4, puppeteer:chunk:5, ... (4 more steps)
      • :chromatic: Upload Storybook to Chromatic
      • :jest: Test (all)
      • :webpack:🌐 Build
      • :webpack:🌐💰 Enterprise build
      • :jest:🌐 Test (client/web)
      • :chrome: Puppeteer tests for chrome extension
      • :jest::chrome: Test (client/browser)
      • :eslint: ESLint
      • :typescript: Build TS
      • :stylelint: Stylelint
    • Go checks
      • :go: Test (all)
      • :go: Test (enterprise/internal/codeintel/stores/dbstore)
      • :go: Test (enterprise/internal/codeintel/stores/lsifstore)
      • :go: Test (enterprise/internal/insights)
      • :go: Test (internal/database)
      • :go: Test (internal/repos)
      • :go: Test (enterprise/internal/batches)
      • :go: Test (cmd/frontend)
      • :go: Test (enterprise/internal/database)
      • :go: Test (enterprise/cmd/frontend/internal/batches/resolvers)
      • :go: Build
    • ⤴️ Upload build trace

• green build