fix typo in network.rst

There is a typo for --domain argument in network create:
Owner’s domain (name or ID)",
the last character " should be removed.

Closes-Bug: #1468282
Change-Id: I81d55841e633a52f3913cf5f4a3e6626ebc1f919

Author: Guojian Shao

doc/source/command-objects/network.rst

@@ -21,7 +21,7 @@ Create new network
 
 .. option:: --domain <domain>
 
-    Owner's domain (name or ID)"
+    Owner's domain (name or ID)
 
 .. option:: --project <project>