fixed label for accessibility

Change-Id: I00785d4edad7cf45340ccaadd96783bf748d9f16
Signed-off-by: Michael Davis <michael.s.davis@ibm.com>
diff --git a/app/common/directives/log-event.html b/app/common/directives/log-event.html
index f36c316..8311a87 100644
--- a/app/common/directives/log-event.html
+++ b/app/common/directives/log-event.html
@@ -29,8 +29,8 @@
                  <p class="inline event__description">{{event.Severity}}</p>
              </div>
          <div class="column small-1 large-1">
-             <button class="accord-trigger" ng-class="{'active': event.meta}"
-                     ng-click="event.meta = ! event.meta"></button>
+             <span class="button accord-trigger" ng-class="{'active': event.meta}"
+                     ng-click="event.meta = ! event.meta" aria-hidden="true"></span>
          </div>
         </div>
      <div class="row event__metadata-row" ng-class="{'active': event.meta}">