Remove a double space from mksyntaxgo for Go folks.

Change-Id: I59fcd7edb4eb1e00535bc8434f1cc0fe458604a4
Reviewed-on: https://code-review.googlesource.com/c/re2/+/58110
Reviewed-by: Paul Wankadia <junyer@google.com>

doc/mksyntaxgo

diff --git a/doc/mksyntaxgo b/doc/mksyntaxgo
index 3df5559..d30d281 100755
--- a/doc/mksyntaxgo
+++ b/doc/mksyntaxgo
@@ -15,7 +15,7 @@
 ,s/\n\n\n+/\n\n/g
 ,x/(^.*	.*\n)+/ | awk -F'	' '{printf("  %-14s %s\n", $1, $2)}'
 1,2c
-// Copyright 2012 The Go Authors.  All rights reserved.
+// Copyright 2012 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.