ssa: fix map key has typeargs

cl/_testgo/syncmap/in.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+func main() {
+	var m sync.Map
+	m.Store(1, "hello")
+	m.Store("1", 100)
+	v, ok := m.Load("1")
+	fmt.Println(v, ok)
+	m.Range(func(k, v interface{}) bool {
+		fmt.Printf("%#v %v\n", k, v)
+		return true
+	})
+}