maint: Fix typos, shebang and simplify a conditional.

* scripts/deploy-packages.sh: Use /usr/bin/env as the shebang as it is
more susceptible to work on all systems (e.g. Guix System).  Fix typo
in header comment.
(package_deb) [qt]: Use a Bash regexp test and an if instead of a case.

Change-Id: Ifa986ddb3bcbea8bacc6af8e510dc64b938588f4