fix: typo (#562)

templates/charms-architecture.html

@@ -64,7 +64,7 @@ <h1 class="p-heading--2">What is a charm?</h1>
           <li class="p-list__item has-bullet"><strong>Controller agent: </strong>a process running workers responsible for a controller. This includes, among others, the Juju API server.</li>
           <li class="p-list__item has-bullet"><strong>Machine agent: </strong>Found on machine clouds, this is a process running workers responsible for a machine.</li>
           <li class="p-list__item has-bullet"><strong>Model agent: </strong>Found on machine and Kubernetes clouds, this is a juju process running workers responsible for all the models associated with a given controller.</li>
-          <li class="p-list__item has-bullet"><strong>Unit agent: </strong>Found on machine and Kubernetes clouds, this isa process responsible for a unit.</li>
+          <li class="p-list__item has-bullet"><strong>Unit agent: </strong>Found on machine and Kubernetes clouds, this is a process responsible for a unit.</li>
         </ul>
       </div>
     </div>