Bump lintrunner mypy dependency to 2.0.0 (#2912)

This updates the lintrunner mypy dependency to the latest release and
keeps repository lint behavior aligned with current mypy tooling. The
change is intentionally scoped to the lintrunner dependency pin.

- **Dependency update**
  - Updated `requirements/lintrunner/requirements.txt`:
    - `mypy==1.10.1` → `mypy==2.0.0`

- **Scope**
  - No production code or test logic changes.
  - No additional mypy ignore configuration changes were required.

```diff
# requirements/lintrunner/requirements.txt
- mypy==1.10.1
+ mypy==2.0.0
```

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: justinchuby <11205048+justinchuby@users.noreply.github.com>

Author: Copilot

requirements/lintrunner/requirements.txt

@@ -3,7 +3,7 @@ lintrunner-adapters>=0.8.0
 # RUFF, RUFF-FIX
 ruff==0.15.1
 # MYPY
-mypy==1.10.1
+mypy==2.0.0
 types-PyYAML==6.0.12.20250915
 # EDITORCONFIG-CHECKER
 editorconfig-checker==3.4.1