Fix typo

src/comm_tiled.cpp

@@ -618,7 +618,7 @@ void CommTiled::reverse_comm()
    atoms exchanged with procs that touch sub-box in each of 3 dims
    send out atoms that have left my box, receive ones entering my box
    atoms will be lost if not inside a touching proc's box
-     can happen if atom moves outside of non-periodic bounary
+     can happen if atom moves outside of non-periodic boundary
      or if atom moves more than one proc away
    this routine called before every reneighboring
    for triclinic, atoms must be in lamda coords (0-1) before exchange is called