test/codegen: fix ARM32 RotateLeft32 test

The syntax of a shifted operation does not have a "$" sign for
the shift amount. Remove it.

Change-Id: I50782fe942b640076f48c2fafea4d3175be8ff99
Reviewed-on: https://go-review.googlesource.com/c/go/+/192100
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

test/codegen/mathbits.go

@@ -208,7 +208,7 @@ func RotateLeft64(n uint64) uint64 {
 
 func RotateLeft32(n uint32) uint32 {
 	// amd64:"ROLL" 386:"ROLL"
-	// arm:`MOVW\tR[0-9]+@>[$]23`
+	// arm:`MOVW\tR[0-9]+@>23`
 	// arm64:"RORW"
 	// ppc64:"ROTLW"
 	// ppc64le:"ROTLW"