man: update os-release(5) to use 24bit ANSI color in example

man: update os-release(5) to use 24bit ANSI color in example

Given that ANSI_COLOR= is mostly about branding it probably makes sense
to use RGB rather than paletted colors for them, so that the colors
match the project design as close as possible. Hence, provide a 25bit
RGB example for ANSI_COLOR, and update the overall example to something
newer.

Also see: https://bugzilla.redhat.com/show_bug.cgi?id=1823099