Fix max number of threads bootstrap docs
Fix max number of threads bootstrap docs

Previously the bootstrap check for max number of threads was increased
from 2048 to 4096 yet the docs were never adjusted for this change. This
commit addresses this so the docs are in-line with the limit enforced in
the bootstrap check.

Relates #27511

vroyer/elasticassandra,strapdata/elassandra,vroyer/elassandra,vroyer/elasticassandra,strapdata/elassandra,strapdata/elassandra,strapdata/elassandra,vroyer/elasticassandra,strapdata/elassandra,vroyer/elassandra,vroyer/elassandra