test: enable inlining tests for functions with local type

Updates #57410

Change-Id: Ibe1f5523a4635d2b844b9a5db94514e07eb0bc0f
Reviewed-on: https://go-review.googlesource.com/c/go/+/463998
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Cuong Manh Le <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Cuong Manh Le <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>

Author: cuonglm

test/escape4.go

@@ -38,20 +38,15 @@ func f2() {} // ERROR "can inline f2"
 func f3() { panic(1) } // ERROR "can inline f3" "1 escapes to heap"
 func f4() { recover() }
 
-// TODO(cuonglm): remove f5, f6 //go:noinline and update the error message
-//                once GOEXPERIMENT=nounified is gone.
-
-//go:noinline
-func f5() *byte {
+func f5() *byte { // ERROR "can inline f5"
 	type T struct {
 		x [1]byte
 	}
 	t := new(T) // ERROR "new.T. escapes to heap"
 	return &t.x[0]
 }
 
-//go:noinline
-func f6() *byte {
+func f6() *byte { // ERROR "can inline f6"
 	type T struct {
 		x struct {
 			y byte