fix(examples): do not overwrite pact file on every test

[individual-it]

✈️ Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

📝 Summary

When overwriting is set to True only the last test-case from that file is saved in the JSON file and the provider side only executes that one test and not all interactions.

🔥 Motivation

run all examples and learn from them

🔨 Test Plan

1. execute examples/tests/v3/test_00_consumer.py before the change
2. expect the count of interactions in examples/pacts/v3_http_consumer-v3_http_provider.json => 1
3. apply the change
4. execute examples/tests/v3/test_00_consumer.py
5. expect the count of interactions in examples/pacts/v3_http_consumer-v3_http_provider.json => 4
6. execute test_01_fastapi_provider.py
7. with fix and improve examples docker compose file #808 run hatch run example

[JP-Ellis]

Amazing thanks for catching this oversight!