trace-cmd: Install completion script in /usr/share/bash-completion/completions

The meson install installs the bash completion in
/usr/share/bash-completion/completions where as the normal "make install"
places the script into /etc/bash_completions.d/. The former is actually
where it should be installed.

Change the make install to place the bash completion script into
/usr/share/bash-completion/completions like the meson install does.

Link: https://lore.kernel.org/20250411090349.09984c9b@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>