[Fix] Update Serving Endpoint mixing template and docs generation logic (#792)

## Changes
Update Serving Endpoint mixing template and docs generation logic

## Tests
<!-- 
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->

- [X] `make test` run locally
- [X] `make fmt` applied
- [ ] relevant integration tests applied

---------

Co-authored-by: Omer Lachish <[email protected]>

Author: hectorcast-db

.codegen/__init__.py.tmpl

@@ -18,7 +18,7 @@ from typing import Optional
   "google_credentials" "google_service_account" }}
 
 {{- define "api" -}}
-  {{- $mixins := dict "ClustersAPI" "ClustersExt" "DbfsAPI" "DbfsExt" "WorkspaceAPI" "WorkspaceExt" "ServingEndpointsExt" "ServingEndpointsApi" -}}
+  {{- $mixins := dict "ClustersAPI" "ClustersExt" "DbfsAPI" "DbfsExt" "WorkspaceAPI" "WorkspaceExt" "ServingEndpointsAPI" "ServingEndpointsExt" -}}
   {{- $genApi := concat .PascalName "API" -}}
   {{- getOrDefault $mixins $genApi $genApi -}}
 {{- end -}}

.codegen/_openapi_sha

@@ -1 +1 @@
-bc17b474818138f19b78a7bea0675707dead2b87
+cf9c61453990df0f9453670f2fe68e1b128647a2