otp-cache: Make -f/--force-update option global

Similar to -v/--verbose of the main program, this change makes the
otp-cache extension's -f/--force-update option a global one, so that it
is accepted at any position and not just before a sub-command.

Author: d-e-s-o

ext/otp_cache.rs

@@ -37,7 +37,7 @@ struct Slot {
 #[structopt(bin_name = "nitrocli otp-cache")]
 struct Args {
   /// Always query the slot data even if it is already cached
-  #[structopt(short, long)]
+  #[structopt(short, long, global = true)]
   force_update: bool,
   #[structopt(subcommand)]
   cmd: Command,