[eos-bash-shared] eos-update: documented option --fast

eos-update

@@ -263,6 +263,8 @@ Options:
   --check-mirrors-eos     Check file $eml for unsupported mirrors.
   --check-mirrors-arch    Check file $aml for unsupported mirrors.
   --edit-mirrorlist       Edit chosen mirrorlist file. Supported: arch, endeavouros. No default.
+  --fast                  Do a fast check for updates in order to reduce the number of database syncs.
+                          Note that this check may not work always even if updates actually are available.
   --nvidia                Check also nvidia driver vs. kernel updates. Useful only with the Nvidia GPU.
   --clear-databases       Clears package database files.
                           Use this only if package database issues constantly make system update fail.