Work with more Debian and Ubuntu variants without altering instructions

This replaces the use of the lsb_release -sc command with dpkg --status tzdata | grep Provides | cut -f2 -d'-' instead, because on Debian and Ubuntu downstream variants, lsb_release -sc will show the codename for the downstream distribution and not the upstream, whereas dpkg --status tzdata | grep Provides | cut -f2 -d'-' will show the correct upstream codename for any downstream distro that uses a merged repository/freestanding repository strategy. This includes popular OS's like Linux Mint Debian Edition, Kali Linux, and Parrot OS. Each of those OS's are OS's I've supported specific user complaints for in this way.

Example error from Parrot OS provided my @mark22k

Err:1 https://deb.i2p2.de ara InRelease                    
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)