Preserve arity for preserving js optional parameters (#37173)

src/compiler/types.ts

@@ -4817,6 +4817,7 @@ namespace ts {
         HasLiteralTypes = 1 << 1,           // Indicates signature is specialized
         IsInnerCallChain = 1 << 2,          // Indicates signature comes from a CallChain nested in an outer OptionalChain
         IsOuterCallChain = 1 << 3,          // Indicates signature comes from a CallChain that is the outermost chain of an optional expression
+        IsUntypedSignatureInJSFile = 1 << 4, // Indicates signature is from a js file and has no types
 
         // We do not propagate `IsInnerCallChain` to instantiated signatures, as that would result in us
         // attempting to add `| undefined` on each recursive call to `getReturnTypeOfSignature` when