install-deps: switch to C.UTF-8 locale

install-deps: switch to C.UTF-8 locale

The en_US.UTF-8 locale is not always going to present on all systems.
Specifically, setting en_US.UTF-8 causes numerous warnings when running
this script on a CentOS Stream 8 container. Rather than install
additional packages to suppress the warning, use the C.UTF-8 locale.

Additionally, try to update the comment explaining the line to something
based on the commit history rather than the confusing term "vulnerable".

Signed-off-by: John Mulligan <jmulligan@redhat.com>