Fix a couple of typos in docker attach docs.

This fix fixes a couple of typos in docker attach docs:
docs/reference/commandline/attach.md
man/docker-attach.1.md

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

docs/reference/commandline/attach.md

@@ -52,7 +52,7 @@ foreground over a slow client connection. Instead, users should use the
 ## Override the detach sequence
 
 If you want, you can configure an override the Docker key sequence for detach.
-This is is useful if the Docker default sequence conflicts with key squence you
+This is useful if the Docker default sequence conflicts with key sequence you
 use for other applications. There are two ways to defines a your own detach key
 sequence, as a per-container override or as a configuration property on  your
 entire configuration.

man/docker-attach.1.md

@@ -44,7 +44,7 @@ attaching to a tty-enabled container (i.e.: launched with `-t`).
 # Override the detach sequence
 
 If you want, you can configure an override the Docker key sequence for detach.
-This is is useful if the Docker default sequence conflicts with key squence you
+This is useful if the Docker default sequence conflicts with key sequence you
 use for other applications. There are two ways to defines a your own detach key
 sequence, as a per-container override or as a configuration property on  your
 entire configuration.