Package required for built-in scripts is wrong in docs

In the Built-In Scripts Hacking Notes it states that scripts must have the package com.onresolve.scriptrunner.canned.jira, but it seems it should be com.onresolve.scriptrunner.canned.jira.admin.

It might also be good to note that the scripts have to be placed in a directory structure that matches the package, since otherwise users might just put them directly in the script root.