patch 8.2.4617: no completion for :scriptnames

Problem:    No completion for :scriptnames.
Solution:   Implement :scriptnames completion. (Yegappan Lakshmanan,
            closes #10005)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index c8ebcf6..e4f9bb0 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -1356,7 +1356,7 @@
 	EX_CMDARG|EX_TRLBAR,
 	ADDR_NONE),
 EXCMD(CMD_scriptnames,	"scriptnames",	ex_scriptnames,
-	EX_BANG|EX_RANGE|EX_COUNT|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
+	EX_BANG|EX_FILES|EX_RANGE|EX_COUNT|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_OTHER),
 EXCMD(CMD_scriptencoding, "scriptencoding", ex_scriptencoding,
 	EX_WORD1|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,