[DOCS] Remove old certgen examples
[DOCS] Remove old certgen examples

Original commit: elastic/x-pack-elasticsearch@68b5eb591e8b904e2c3ba76ba9bc6e724c605869

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