cli: drop unnecessary NULL sentinel from nmc_complete_strings()

Since commit 62b939de4e ('cli: add nmc_complete_strv() which takes a
string array for completion that may contain NULL'), the sentinel is
no longer needed.

clients/cli/nmcli.c

@@ -732,7 +732,7 @@ process_command_line (NmCli *nmc, int argc, char **argv)
 			nmc_complete_strings (argv[0], "--terse", "--pretty", "--mode", "--overview",
 			                               "--colors", "--escape",
 			                               "--fields", "--nocheck", "--get-values",
-			                               "--wait", "--version", "--help", NULL);
+			                               "--wait", "--version", "--help");
 		}
 
 		if (argv[0][1] == '-' && argv[0][2] == '\0') {