types(Interaction): allow Interaction cached properties to be type narrowed (#6668)

Co-authored-by: Sugden <28943913+NotSugden@users.noreply.github.com>
Co-authored-by: Rodry <38259440+ImRodry@users.noreply.github.com>
Co-authored-by: Antonio Román <kyradiscord@gmail.com>

tslint.json

@@ -22,7 +22,7 @@
     "member-access": true,
     "no-unnecessary-class": false,
     "array-type": [true, "array"],
-
+    "one-line": false,
     "no-any-union": false,
     "void-return": false
   }