Better describe what /repos/{owner}/{repo}/raw/{filepath} returns on 200 (#19542)

- Set on the description that it returns the raw file content.
- Resolves #19514

templates/swagger/v1_json.tmpl

@@ -8628,7 +8628,7 @@
         ],
         "responses": {
           "200": {
-            "description": "success"
+            "description": "Returns raw file content."
           },
           "404": {
             "$ref": "#/responses/notFound"