[InlineAdvisor] Remove outdated comment (NFC)

This just returns None nowadays, so this comment doesn't apply
anymore.

llvm/lib/Analysis/InlineAdvisor.cpp

@@ -409,8 +409,6 @@ llvm::shouldInline(CallBase &CB,
              << "' in other contexts";
     });
     setInlineRemark(CB, "deferred");
-    // IC does not bool() to false, so get an InlineCost that will.
-    // This will not be inspected to make an error message.
     return None;
   }