Fix spelling mistakes

src/tree.c

@@ -477,7 +477,7 @@ static void mark_unmapped(Con *con) {
     TAILQ_FOREACH(current, &(con->nodes_head), nodes)
     mark_unmapped(current);
     if (con->type == CT_WORKSPACE) {
-        /* We need to call mark_unmapped on floating nodes aswell since we can
+        /* We need to call mark_unmapped on floating nodes as well since we can
          * make containers floating. */
         TAILQ_FOREACH(current, &(con->floating_head), floating_windows)
         mark_unmapped(current);