Bump flit from 3.7.1 to 3.9.0

Bumps [flit](https://github.com/pypa/flit) from 3.7.1 to 3.9.0.
- [Changelog](https://github.com/pypa/flit/blob/main/doc/history.rst)
- [Commits](pypa/flit@3.7.1...3.9.0)

---
updated-dependencies:
- dependency-name: flit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -61,7 +61,7 @@ test = [
     "yapf >=0.29.0",
 ]
 dev = [
-    "flit ==3.7.1",
+    "flit ==3.9.0",
     "build ==0.7.0",
     "yapf >=0.29.0",
     "pyyaml >=5.3",