fix(deps): allow higher version of `importlib-resources` for python 3.9 and above

[aberlioz]

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The pin on version ^5.12.0 of package importlib-resources was introduced in this PR: https://github.com/wiremock/python-wiremock/pull/60

It prevents applications running on higher versions of python to install the newest importlib-resources versions.

Considering the usage of the lib, one can argue that we don't even need this dependencies for python version 3.9 and above.

References

• https://github.com/wiremock/python-wiremock/pull/60

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