test/typeparam: fix issue48094b test build

CL 347529 broke the longtest builders due to missing -G=3 flag when
compiling the added test.

Change-Id: I73007801dd6871a8cf3554e957d247f5f56fd641
Reviewed-on: https://go-review.googlesource.com/c/go/+/348330
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>

test/typeparam/issue48094b.go

@@ -1,4 +1,4 @@
-// compiledir
+// compiledir -G=3
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style