fix: write_pact_file was always serialising a v3 pact even if the spec version was set to 2
fix: write_pact_file was always serialising a v3 pact even if the spec version was set to 2

pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-mock-server,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference,pact-foundation/pact-reference