Do not annotate bare type parameters as @Nullable

This is to account for the case of, say

     class Function<R> { fun invoke(): R }

it would be a shame to put @Nullable on the return type of the function, and force all callers to check for null,
so we put no annotations

compiler/testData/asJava/nullabilityAnnotations/Generic.kt

@@ -0,0 +1,7 @@
+trait Generic<N, NN: Any> {
+    fun a(n: N): N
+    fun b(nn: NN): NN
+
+    fun a1(n: N?): N?
+    fun b1(nn: NN?): NN?
+}