cmd/compile: regenerate known formats in fmtmap_test.go

This fixes TestFormats after CL 192278.

Change-Id: I7ffb8f76b4f6469d1b161d41687306e0d9e7abd1
Reviewed-on: https://go-review.googlesource.com/c/go/+/191786
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/fmtmap_test.go

@@ -189,6 +189,7 @@ var knownFormats = map[string]string{
 	"uint %x":              "",
 	"uint16 %d":            "",
 	"uint16 %x":            "",
+	"uint32 %#U":           "",
 	"uint32 %#x":           "",
 	"uint32 %d":            "",
 	"uint32 %v":            "",