Docs for keystore commands for email and jira actions incorrect

[eskibars]

The documentation for the email and jira actions for Watcher (https://www.elastic.co/guide/en/elastic-stack-overview/6.6/actions-email.html#gmail and https://www.elastic.co/guide/en/elastic-stack-overview/6.6/actions-jira.html)

leaves off the add part of the command. For example, the docs on both of these pages read:

bin/elasticsearch-keystore xpack.notification.email.account.gmail_account.smtp.secure_password

when they should read somethind like

bin/elasticsearch-keystore add xpack.notification.email.account.gmail_account.smtp.secure_password

[elasticmachine]

Pinging @elastic/es-core-features