[9.1] Remove incorrectly added EsqlCapability (elastic#131963)

Accidentally added this in when backporting elastic#131954 which will break
some of the tests, so I am removing it

Author: limotova

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -910,11 +910,6 @@ public enum Cap {
          */
         AGGREGATE_METRIC_DOUBLE_AVG(AGGREGATE_METRIC_DOUBLE_FEATURE_FLAG),
 
-        /**
-         * Support for implicit casting of aggregate metric double when run in aggregations
-         */
-        AGGREGATE_METRIC_DOUBLE_IMPLICIT_CASTING_IN_AGGS(AGGREGATE_METRIC_DOUBLE_FEATURE_FLAG),
-
         /**
          * Fixes bug when aggregate metric double is encoded as a single nul value but decoded as
          * AggregateMetricDoubleBlock (expecting 4 values) in TopN.