[DOCS] Drafted 6.2.1 security release notes (elastic/x-pack-elasticsearch#3873)
[DOCS] Drafted 6.2.1 security release notes (elastic/x-pack-elasticsearch#3873)

Original commit: elastic/x-pack-elasticsearch@61e3f0cd993f78529f673e3d425dc92d0e99b60a

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