pages.it/*: update path placeholders and "directory" translations (#9031)

- Replace "al" -> "del", "alla" -> "della", etc. in command paths
- Replace all instances of "cartella" with "directory"
- Update contributing-guides/translation-templates/common-arguments.md to
  reflect these changes

Co-authored-by: marchersimon <50295997+marchersimon@users.noreply.github.com>
Co-authored-by: Marco Bonelli <marco@mebeim.net>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages.it/common/git-am.md

@@ -6,7 +6,7 @@
 
 - Applica un file di patch:
 
-`git am {{percorso/al/file.patch}}`
+`git am {{percorso/del/file.patch}}`
 
 - Interrompi l'applicazione di un file di patch:
 
@@ -14,4 +14,4 @@
 
 - Applica quanto possibile di un file di patch, salvando le parti non applicabili in file `.rej`:
 
-`git am --reject {{percorso/al/file.patch}}`
+`git am --reject {{percorso/del/file.patch}}`