AC-7116: Removed default engine value as ES7 will be the default search engine for 2.4.6

Author: faizan-shk

app/code/Magento/Elasticsearch8/etc/config.xml

@@ -9,7 +9,6 @@
     <default>
         <catalog>
             <search>
-                <engine>elasticsearch8</engine>
                 <elasticsearch8_server_hostname>localhost</elasticsearch8_server_hostname>
                 <elasticsearch8_server_port>9200</elasticsearch8_server_port>
                 <elasticsearch8_index_prefix>magento2</elasticsearch8_index_prefix>