Fix interconnect direction doc string for usnistgov#1913

The information appears to repeat information about a related prop name
regarding IPv6 connectivity.

src/metaschema/oscal_implementation-common_metaschema.xml

@@ -194,7 +194,7 @@
                         <enum value="isa-remote-system-name">The name of the remote interconnected system.</enum>
                         <enum value="ipv4-address">An Internet Protocol Version 4 interconnection address</enum>
                         <enum value="ipv6-address">An Internet Protocol Version 6 interconnection address</enum>
-                        <enum value="direction">An Internet Protocol Version 6 interconnection address</enum>
+                        <enum value="direction">The direction of network connectivity for the interconnection address</enum>
                   </allowed-values>
                   <allowed-values target="prop[has-oscal-namespace('http://csrc.nist.gov/ns/oscal') and @name=('ipv4-address','ipv6-address')]/@class">
                         <enum value="local">The identified IP address is for this system.</enum>