More read-only-allow-delete docs (#45320)
More read-only-allow-delete docs (#45320)

Adds to the `index.blocks.read_only_allow_delete` docs the information that
this block may be added or removed automatically.

Relates #42559

robin13/elasticsearch,uschindler/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,gingerwizard/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,HonzaKral/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch