workqueue: Correct/Drop references to gcwq in Documentation

No functional changes. This patch fixes the post gcwq comments in
Documentation/workqueue.txt.

tj: Whitespace adjustments.  Minor updates.

Signed-off-by: Libin <huawei.libin@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
1 file changed