cmd/compile: fix fmt test

CL 196781 added map[int64]uint32 to the set of things printed with %v.

Fixes #34907

Change-Id: If4a13e86cfb4b691988f5fb70449ae23760f5789
Reviewed-on: https://go-review.googlesource.com/c/go/+/201079
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/fmtmap_test.go

@@ -171,6 +171,7 @@ var knownFormats = map[string]string{
 	"map[*cmd/compile/internal/gc.Node]*cmd/compile/internal/ssa.Value %v": "",
 	"map[*cmd/compile/internal/gc.Node][]*cmd/compile/internal/gc.Node %v": "",
 	"map[cmd/compile/internal/ssa.ID]uint32 %v":                            "",
+	"map[int64]uint32 %v":                                                  "",
 	"math/big.Accuracy %s":                                                 "",
 	"reflect.Type %s":                                                      "",
 	"rune %#U":                                                             "",