fix Missing 404 swagger response docs for /admin/users/{username} (#26086)

close #26079

templates/swagger/v1_json.tmpl

@@ -620,6 +620,9 @@
           "403": {
             "$ref": "#/responses/forbidden"
           },
+          "404": {
+            "$ref": "#/responses/notFound"
+          },
           "422": {
             "$ref": "#/responses/validationError"
           }