update "artists" link url

vue-theme/src/components/navigation/navigation.vue

                     li
                         router-link(to="/technique") Techniques
             li.f-grow
-                router-link(to="/artist/") Artists
+                router-link(to="/artist") Artists
                 ul.submenu
                     li
                         router-link(to="/artist/sorted/by-alpha") A - Z
                     li
                         router-link(to="/artist/sorted/by-material") By Material
             li.f-grow 
-                router-link(to="/exhibition/") Exhibitions
+                router-link(to="/exhibition") Exhibitions
                 ul.submenu 
                     li
                         router-link(to="/exhibition/sorted/by-current-and-upcoming") Current/Upcoming