[Docs] Add SFS constraint for AR
[Docs] Add SFS constraint for AR

Documented the SFS backup constraint
for AR products

Resolves: LE-11637
Change-Id: Ibdc4f5aff2f36a2ff24ee3707dfda4d11851b77d

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af