all: use typed variant of protoreflect.ValueOf

Change-Id: I7479632b57e7c8efade12a2eb2b855e9c321adb1
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/196037
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/impl/convert_map.go b/internal/impl/convert_map.go
index 47b5f22..2ddfc78 100644
--- a/internal/impl/convert_map.go
+++ b/internal/impl/convert_map.go
@@ -31,7 +31,7 @@
 	if v.Type() != c.goType {
 		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
 	}
-	return pref.ValueOf(&mapReflect{v, c.keyConv, c.valConv})
+	return pref.ValueOfMap(&mapReflect{v, c.keyConv, c.valConv})
 }
 
 func (c *mapConverter) GoValueOf(v pref.Value) reflect.Value {