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

  663 files  +  663    663 suites  +663   45s ⏱️ +45s
2 228 tests +2 228  1 665 ✅ +1 665  563 💤 +563  0 ❌ ±0 
2 236 runs  +2 236  1 673 ✅ +1 673  563 💤 +563  0 ❌ ±0 

Results for commit 4f53635. ± Comparison against base commit 58c419e.

♻️ This comment has been updated with latest results.