Remove all document variables hint

[temaEmelyan]

Please make sure you consider the following:

• Add tests that use __typename in queries
• Does this change work with all nadel transformations (rename, type rename, hydration, etc)? Add tests for this.
• Is it worth using hints for this change in order to be able to enable a percentage rollout?
• Do we need to add integration tests for this change in the graphql gateway?
• Do we need a pollinator check for this?

[github-actions]

Test Results

  658 files  +  658    658 suites  +658   1m 5s ⏱️ + 1m 5s
1 989 tests +1 989  1 431 ✅ +1 431  558 💤 +558  0 ❌ ±0 
1 997 runs  +1 997  1 439 ✅ +1 439  558 💤 +558  0 ❌ ±0 

Results for commit 6d33f8c. ± Comparison against base commit 160ccad.

♻️ This comment has been updated with latest results.