go/printer: remove package comment from testdata/parser.go

This prevents an incorrect summary line from appearing in the godoc
package list.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5607059

src/pkg/go/printer/testdata/parser.go

@@ -6,7 +6,7 @@
 // provided in a variety of forms (see the various Parse* functions); the
 // output is an abstract syntax tree (AST) representing the Go source. The
 // parser is invoked through one of the Parse* functions.
-//
+
 package parser
 
 import (