chore: Remove obsolete rule-engine configuration (#19910)

We forgot to remove `system.program_rule.server_execution` configuration that was only used by old tracker API.
In Tracker API the same behavior is now achieved using `skipRuleEngine` (https://docs.dhis2.org/en/develop/using-the-api/dhis-core-version-master/tracker.html#webapi_tracker_import_request_parameters)

dhis-2/dhis-support/dhis-support-external/src/main/java/org/hisp/dhis/external/conf/ConfigurationKey.java

@@ -60,12 +60,6 @@ public enum ConfigurationKey {
   /** SQL view write enabled, can be 'on', 'off'. (default: off) */
   SYSTEM_SQL_VIEW_WRITE_ENABLED("system.sql_view_write_enabled", Constants.OFF, false),
 
-  /**
-   * Disable server-side program rule execution, can be 'on', 'off'. <br>
-   * (default: on)
-   */
-  SYSTEM_PROGRAM_RULE_SERVER_EXECUTION("system.program_rule.server_execution", Constants.ON, false),
-
   /**
    * Set the maximum size for the cache instance to be built. If set to 0, no caching will take
    * place. Cannot be a negative value. (default: 0).