chore(deps-dev): update flit-core requirement

Updates the requirements on [flit-core](https://github.com/pypa/flit) to permit the latest version.
- [Changelog](https://github.com/pypa/flit/blob/main/doc/history.rst)
- [Commits](pypa/flit@3.2.0...3.12.0)

---
updated-dependencies:
- dependency-name: flit-core
  dependency-version: 3.12.0
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -1,7 +1,7 @@
 # https://setuptools.pypa.io/en/latest/userguide/pyproject_config.html
 # https://flit.pypa.io/en/latest/pyproject_toml.html
 [build-system]
-requires = ["flit_core >=3.2.0,<4.0.0"]
+requires = ["flit_core >=3.12.0,<4.0.0"]
 build-backend = "flit_core.buildapi"
 
 [project]