Update mypy requirement from ~=1.7.0 to >=1.7,<1.9 (#137)

Updates the requirements on [mypy](https://github.com/python/mypy) to permit the latest version.
- [Changelog](https://github.com/python/mypy/blob/master/CHANGELOG.md)
- [Commits](python/mypy@v1.7.0...v1.8.0)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pyproject.toml

@@ -35,7 +35,7 @@ zulip = [
 tests = [
     "pytest~=7.4.3",
     "types-PyYAML~=6.0.12",
-    "mypy~=1.7.0"
+    "mypy>=1.7,<1.9"
 ]
 
 [project.scripts]