[skip ci ] Adjust warning messages to align with style of other const…

…raints

src/validations/constraints/fedramp-external-constraints.xml

@@ -161,10 +161,10 @@
                 <message>A FedRAMP SSP must define a role for the point of contact for an information system security officer.</message>
             </expect>
             <expect id="party-has-responsibility" target="." test="every $person in //party[@type='person'] satisfies exists(.//responsible-party[party-uuid = $person/@uuid])" level="WARNING">
-                <message>One or more persons do not have any assigned responsibilities.</message>
+                <message>Every party in a FedRAMP SSP must be responsible for a role.</message>
             </expect>
             <expect id="party-has-one-responsibility" target="." test="every $person in //party[@type='person'] satisfies count(.//responsible-party[party-uuid = $person/@uuid]) eq 1" level="WARNING">
-                <message>One or more persons have multiple assigned responsibilities.</message>
+                <message>Every party in a FedRAMP SSP must be responsible for only one role.</message>
             </expect>
         </constraints>
     </context>