Update rest-api-spec (#4915)

Co-authored-by: pquentin <[email protected]>

Author: github-actions[bot]

output/schema/validation-errors.json

@@ -279,12 +279,6 @@
       ],
       "response": []
     },
-    "search_mvt": {
-      "request": [
-        "Request: query parameter 'grid_agg' does not exist in the json spec"
-      ],
-      "response": []
-    },
     "searchable_snapshots.clear_cache": {
       "request": [
         "Request: missing json spec query parameter 'index'"

specification/_json_spec/search_mvt.json

@@ -62,6 +62,12 @@
         "description": "Determines the geometry type for features in the aggs layer.",
         "default": "grid"
       },
+      "grid_agg": {
+        "type": "enum",
+        "options": ["geotile", "geohex"],
+        "description": "Aggregation used to create a grid for `field`.",
+        "default": "geotile"
+      },
       "size": {
         "type": "int",
         "description": "Maximum number of features to return in the hits layer. Accepts 0-10000.",