docs(CONTRIBUTING.md): update installation steps

adds step to patch the compatibility suite in order for tests to pass

CONTRIBUTING.md

@@ -101,9 +101,11 @@ You can also try using the new [github.dev](https://github.dev/pact-foundation/p
 
 3.  After cloning the repository, run `hatch shell` in the root of the repository. This will install all dependencies in a Python virtual environment and then ensure that the virtual environment is activated. You will also need to run `git submodule init` if you want to run tests, as Pact Python makes use of the Pact Compability Suite.
 
-4.  To run tests, run `hatch run test` to make sure the test suite is working. You should also make sure the example works by running `hatch run example`. For the examples, you will have to make sure that you have Docker (or a suitable alternative) installed and running.
+4.  Patch the compatibility suite by running `cd tests/v3/compatibility_suite && patch -p1 -d definition < definition-update.diff && cd -` in the root of the repository.
 
-5.  If you want to run the tests against all supported Python versions, you can run `hatch run test:all`.
+5.  To run tests, run `hatch run test` to make sure the test suite is working. You should also make sure the example works by running `hatch run example`. For the examples, you will have to make sure that you have Docker (or a suitable alternative) installed and running.
+
+6.  If you want to run the tests against all supported Python versions, you can run `hatch run test:all`.
 
 ### Code Conventions