Update ci-fix.md add apiReadinessCheck (#20061)

* Update ci-fix.md

* Update ci-fix.md

Minor change on wording.

Co-authored-by: Ray Chen <raychen@microsoft.com>

documentation/ci-fix.md

@@ -109,6 +109,15 @@ Note: When running in Swagger PR pipeline, Avocado only report errors with file
 
 Refer to [Avocado Readme](https://github.com/Azure/avocado/blob/master/README.md) for detailed description of validations and how-to-fix guidance.
 
+## API Readiness Check
+
+This CI check is to make sure service is ready before PR merge. Technically, the CI check send operationsList HTTP request to Azure Resource Provider. 
+
+To fix this CI check failure, if you haven't got ARM signed off, pls get ARM signed off first then deploy ARM manifest. After deploying ARM manifest, this operationsList HTTP request will succeed and CI pass.
+
+NOTE: If your RP is RPaaS RP, since RPaaS requires swagger merge first. In this case, you could ignore this CI check.
+
+
 ## Service API Readiness Test
 
 This CI check is to test service API readiness, by running API Scenario test to verify: