Update flit-core requirement from <4,>=2 to >=3.12.0,<4 (#587)

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

Author: dependabot[bot]

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core >=2,<4"]
+requires = ["flit_core >=3.12.0,<4"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.metadata]