fix(css): fix css justify-content property's value 'start, end' has mixed support warning

src/components/alerts/inline-message.css

@@ -5,7 +5,7 @@
     color: $ui-white;
     font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
     display: flex;
-    justify-content: end;
+    justify-content: flex-end;
     align-items: center;
     font-size: .8125rem;
 }

src/components/menu-bar/author-info.css

@@ -5,7 +5,7 @@
     color: $ui-white;
     font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
     display: flex;
-    justify-content: start;
+    justify-content: flex-start;
     align-items: center;
     cursor: default;
 }