…nstead of checking preview disabled directly (#23950)

Minor followup to #23845 - I forgot one spot where we should use the
`preview.rs` function instead of `preview.is_disabled()`.

* main: (131 commits)
  [ty] Fixup examples in `invalid-key` docs (#23968)
  [ty] Fix compiler warning about unused variable (#23967)
  [ty] Sync vendored typeshed stubs (#23963)
  Add a `.git-blame-ignore-revs` file (#23959)
  Revert "[ty] Completely remove the `NoReturn` shortcut optimization" (#23955)
  [ty] Completely remove the `NoReturn` shortcut optimization (#23378)
  [ty] Introduce fast path for protocol non-assignability (#23952)
  Bump typing conformance suite SHA (#23951)
  Minor followup to severity display - use preview function in server instead of checking preview disabled directly (#23950)
  Document editor features for markdown code formatting (#23924)
  [ty] Add `with_recursion_guard()` helpers to `relation.rs` (#23945)
  [ty] Remove `check_optional_method_pair` methods (#23947)
  [ty] Remove unused `CycleDetector::try_visit` method (#23944)
  [ty] Ensure TypedDict subscripts for unknown keys return Unknown (#23926)
  [ty] Fix variance of frozen dataclass-transform models (#23931)
  Display output severity in preview (#23845)
  Revert "[`ruff`] use `bitcode` instead of `bincode`" (#23935)
  Fix shell injection via `shell=True` in subprocess calls (#23894)
  [ty] Refactor `relation.rs` to store state on a struct rather than passing around 7 arguments every time we recurse (#23837)
  Don't return code actions for non-Python documents (#23905)
  ...