fix: make description in Item Search openapi GET/POST impl consistent with README (#168)

Author: philvarner

item-search/openapi.yaml

@@ -23,8 +23,7 @@ paths:
         Retrieve Items matching filters. Intended as a shorthand API for simple
         queries.
 
-        This method is optional, but you MUST implement `POST /search` if you
-        want to implement this method.
+        This method is required to implement.
 
         If this endpoint is implemented on a server, it is required to add a
         link referring to this endpoint with `rel` set to `search` to the
@@ -62,10 +61,11 @@ paths:
       summary: Search STAC items with full-featured filtering.
       operationId: postItemSearch
       description: |-
-        retrieve items matching filters. Intended as the standard, full-featured
+        Retrieve items matching filters. Intended as the standard, full-featured
         query API.
 
-        This method is mandatory to implement if `GET /search` is implemented.
+        This method is optional to implement, but recommended.
+
         If this endpoint is implemented on a server, it is required to add a
         link referring to this endpoint with `rel` set to `search` and `method`
         set to `POST` to the `links` array in `GET /`.