Rely on default shard count (elastic#120369) (elastic#120377)

Author: idegtiarenko

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/esql/190_lookup_join.yml

@@ -25,7 +25,6 @@ setup:
           settings:
             index:
               mode: lookup
-            number_of_shards: 1
           mappings:
             properties:
               key: