Switch visibility to public in ESQL REST spec (elastic#100622) (elast…

…ic#100628)

This update the visibility field in ESQL's REST spec to public.

It also updates the types of quotes used for one the REST object
parameter to backticks, for consistency.

rest-api-spec/src/main/resources/rest-api-spec/api/esql.query.json

@@ -5,7 +5,7 @@
       "description":"Executes an ESQL request"
     },
     "stability":"experimental",
-    "visibility":"private",
+    "visibility":"public",
     "headers":{
       "accept": [ "application/json"],
       "content_type": ["application/json"]
@@ -32,7 +32,7 @@
       }
     },
     "body":{
-      "description":"Use the `query` element to start a query. Use `time_zone` to specify an execution time zone and 'columnar' to format the answer.",
+      "description":"Use the `query` element to start a query. Use `time_zone` to specify an execution time zone and `columnar` to format the answer.",
       "required":true
     }
   }