Update migrating.md

manual/src/migrating.md

@@ -3,7 +3,7 @@
 ## Notable changes
  - Arrays are full-class citizens, using the @ sigil. That means emails and git urls must be single quoted
  - The shell has proper scopes (variables get unset after the end of the definition scope), and functions are closures
- - The shell has an internal variable store. That means environment variables must be explicitely exported to be available to commands.
+ - The shell has an internal variable store. That means environment variables must be explicitly exported to be available to commands.
  - For now, per-command environment variables are not supported (ex: `LANG=it_CH.utf8 man man`)
  - The testing builtin (`[[ .. ]]`) was replaced with `test`, `exists`, and/or other commands
  - The control flow have been revisited, see the relevant part of the manual