BUG/MINOR: checks: Remove wrong variable redeclaration

When mysql-check option is parsed, the user variable is redeclared without any
reason. thus the redeclared variable is removed.

No backport needed.
diff --git a/src/checks.c b/src/checks.c
index 4279290..774b28c 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -6340,7 +6340,6 @@
 
 	cur_arg += 2;
 	if (*args[cur_arg]) {
-		char *user;
 		int packetlen, userlen;
 
 		if (strcmp(args[cur_arg], "user") != 0) {