all: make copyright headers consistent with one space after period

Follows suit with https://go-review.googlesource.com/#/c/20111.

Generated by running
$ grep -R 'Go Authors.  All' * | cut -d":" -f1 | while read F;do perl -pi -e 's/Go
Authors.  All/Go Authors. All/g' $F;done

The code in cmd/internal/unvendor wasn't changed.

Fixes #15213

Change-Id: I4f235cee0a62ec435f9e8540a1ec08ae03b1a75f
Reviewed-on: https://go-review.googlesource.com/21819
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

test/interface/recursive1.dir/recursive1.go

diff --git a/test/interface/recursive1.dir/recursive1.go b/test/interface/recursive1.dir/recursive1.go
index 441f0ec..8498cb5 100644
--- a/test/interface/recursive1.dir/recursive1.go
+++ b/test/interface/recursive1.dir/recursive1.go
@@ -1,4 +1,4 @@
-// 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.
 

test/interface/recursive1.dir/recursive2.go

diff --git a/test/interface/recursive1.dir/recursive2.go b/test/interface/recursive1.dir/recursive2.go
index e8048c6..29385df 100644
--- a/test/interface/recursive1.dir/recursive2.go
+++ b/test/interface/recursive1.dir/recursive2.go
@@ -1,4 +1,4 @@
-// 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.