Update flit-core requirement in the actions group (#86)

Updates the requirements on [flit-core](https://github.com/pypa/flit) to permit the latest version.

Updates `flit-core` to 4.0.2
- [Changelog](https://github.com/pypa/flit/blob/main/doc/history.rst)
- [Commits](pypa/flit@3.2.0...4.0.2)

---
updated-dependencies:
- dependency-name: flit-core
  dependency-version: 4.0.2
  dependency-type: direct:development
  dependency-group: actions
...

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

Author: dependabot[bot]

pyproject.toml

@@ -4,7 +4,7 @@
 
 [build-system]
 build-backend = "flit_core.buildapi"
-requires = ["flit_core >=3.2,<4"]
+requires = ["flit_core >=3.2,<5"]
 
 [project]
 authors = [{name = "Kevin Meagher"}]