Correct the size of tmp array

The snprintf using it should work with any int, which means this string
has to fit ",-2147483648\0", which is 12 characters + a null terminator.

Otherwise it could lead to a buffer overflow, corrupting other variables
on the stack, and maybe causing a crash too?

pg_stat_monitor.c

@@ -3774,7 +3774,7 @@ intarray_get_datum(int32 arr[], int len)
 {
 	int			j;
 	char		str[1024];
-	char		tmp[10];
+	char		tmp[13];
 
 	str[0] = '\0';