Enable caching of `uv`

[JP-Ellis]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Description

Enable caching of uv in CI once the following upstream PR is merged:

• Add support for caching uv actions/setup-python#818

Has this been requested on Canny?

No response

Motivation

This will speed up the CI pipelines by avoiding unnecessary downloads.

Have you tried building it?

No response

Self-service

• I'd be willing to contribute this feature to Pact Python myself.

[JP-Ellis]

Has been implemented as part of #819