Add .infrahub.yml config file to conflict-01 test fixture

The conflict-01 test fixture was missing a .infrahub.yml configuration
file. With the new RepositoryConfigurationError exception that is now
raised when a repository lacks this config file, the integration tests
using this fixture were failing.

This adds a minimal .infrahub.yml to fix the integration tests:
- test_run_pipeline_validate_requested_jobs
- test_run_generators_validate_requested_jobs

Author: petercrocker

backend/tests/fixtures/repos/conflict-01/initial__main/.infrahub.yml

@@ -0,0 +1,3 @@
+# yaml-language-server: $schema=https://schema.infrahub.app/python-sdk/repository-config/develop.json
+---
+# Minimal configuration for test repository