[Synapse]Fix Credential OperationId Not UnifiedIssue

Author: Jingshu918

specification/synapse/data-plane/Microsoft.Synapse/stable/2020-12-01/credential.json

@@ -31,7 +31,7 @@
         "tags": [
           "credentials"
         ],
-        "operationId": "Credentials_ListByWorkspace",
+        "operationId": "Credential_ListByWorkspace",
         "x-ms-examples": {
           "Credentials_ListByWorkspace": {
             "$ref": "./examples/Credentials_ListByWorkspace.json"
@@ -67,7 +67,7 @@
         "tags": [
           "credentials"
         ],
-        "operationId": "Credentials_CreateOrUpdate",
+        "operationId": "Credential_CreateOrUpdate",
         "x-ms-examples": {
           "Credentials_Create": {
             "$ref": "./examples/Credentials_Create.json"