chore(npm): update istanbul dependency
chore(npm): update istanbul dependency

Cleanup the unit_coverage instruction at the same time

lucisilv/Silviu_S3-Antidote,scality/S3,tomateos/S3,truststamp/S3,lucisilv/Silviu_S3-Antidote,truststamp/S3,lucisilv/Silviu_S3-Antidote,scality/S3,scality/S3,scality/S3,tomateos/S3,lucisilv/Silviu_S3-Antidote,truststamp/S3,tomateos/S3,lucisilv/Silviu_S3-Antidote,lucisilv/Silviu_S3-Antidote,truststamp/S3,truststamp/S3,lucisilv/Silviu_S3-Antidote,scality/S3,tomateos/S3,lucisilv/Silviu_S3-Antidote,scality/S3,truststamp/S3,tomateos/S3,scality/S3,truststamp/S3,scality/S3,tomateos/S3,tomateos/S3,truststamp/S3,tomateos/S3