[Docs] Update le_appCtrl typo
[Docs] Update le_appCtrl typo

Replaced StartApp with Start as per the function call.

Resolves: LE-7442
Change-Id: Ib128f5043e14fcc06aa58880883992a0c54ed568

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