[DOCS] Add force merge to hot phase list (#61725) (#61730)

Author: jrodewig

docs/reference/ilm/ilm-index-lifecycle.asciidoc

@@ -77,6 +77,7 @@ the rollover criteria, it could be 20 minutes before the rollover is complete.
 * Hot
   - <<ilm-set-priority,Set Priority>>
   - <<ilm-unfollow,Unfollow>>
+  - <<ilm-forcemerge,Force Merge>>
   - <<ilm-rollover,Rollover>>
 * Warm
   - <<ilm-set-priority,Set Priority>>