add --hours= option to docs (#8541)

* Update passport.md

add  --hours= options to docs

* Update passport.md

---------

Co-authored-by: Taylor Otwell <[email protected]>

Author: Safemood

passport.md

@@ -551,6 +551,9 @@ When tokens have been revoked or expired, you might want to purge them from the
 # Purge revoked and expired tokens and auth codes...
 php artisan passport:purge
 
+# Only purge tokens expired for more than 6 hours...
+php artisan passport:purge --hours=6
+
 # Only purge revoked tokens and auth codes...
 php artisan passport:purge --revoked