patch 8.0.0560: :windo allows for ! but it's not supported

Problem:    :windo allows for ! but it's not supported.
Solution:   Disallow passing !. (Hirohito Higashi)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 88dfbb9..531bd0e 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -1623,7 +1623,7 @@
 			NEEDARG|WORD1|RANGE|NOTADR,
 			ADDR_WINDOWS),
 EX(CMD_windo,		"windo",	ex_listdo,
-			BANG|NEEDARG|EXTRA|NOTRLCOM|RANGE|NOTADR|DFLALL,
+			NEEDARG|EXTRA|NOTRLCOM|RANGE|NOTADR|DFLALL,
 			ADDR_WINDOWS),
 EX(CMD_winpos,		"winpos",	ex_winpos,
 			EXTRA|TRLBAR|CMDWIN,