fmt: remove unused global variable byteType

Change list https://golang.org/cl/20686/ removed the last use
of the variable byteType.

Change-Id: I4ea79095136a49a9d22767b37f48f3404da05056
Reviewed-on: https://go-review.googlesource.com/37197
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/fmt/print.go

@@ -684,8 +684,6 @@ func (p *pp) printArg(arg interface{}, verb rune) {
 	}
 }
 
-var byteType = reflect.TypeOf(byte(0))
-
 // printValue is similar to printArg but starts with a reflect value, not an interface{} value.
 // It does not handle 'p' and 'T' verbs because these should have been already handled by printArg.
 func (p *pp) printValue(value reflect.Value, verb rune, depth int) {