[PutRequestResponseSchemeArm] False positive due to bug in utils.isSchemaEqual()

[mikeharder]

In this check run, run PutRequestResponseSchemeArm appears to fail with a false positive, since the schemas are indeed identical. I believe the bug is in helper function utils.isSchemaEqual():

https://github.com/Azure/azure-openapi-validator/blob/edb65591d5ab85871f880e48b2ad6302186014b8/packages/rulesets/src/spectral/functions/utils.ts

Even if the schemas are equal, if one of the property values is null, it will cause isSchemaEqual() to fail, which looks like a bug to me. Unless there's some reason this behavior was chosen intentionally.