Remove testing Kotlin signature from WriteSignatureTest

compiler/testData/writeSignature/VarargGeneric.kt

@@ -2,7 +2,4 @@ fun <P> foo(vararg tail: P) = 1
 
 // method: _DefaultPackage::foo
 // jvm signature:     ([Ljava/lang/Object;)I
-// generic signature: <P:Ljava/lang/Object;>([TP;)I
-// kotlin signature:  <erased P:?Ljava/lang/Object;>([TP;)I
-// TODO: skip kotlin signature
-// TODO: properly serialize typeinfo
+// generic signature: <P:Ljava/lang/Object;>([TP;)I