Update index.md (#7211)

updated the command to not include backreference:
Because:
The pattern is trying to match a log line where the hour, minute, and second are equal to the day of the month (e.g., [10/Mar/2025:10:10:10).
This is very unusual and restrictive for Fail2ban and might only match some synthetic or test logs, not real-world ones.

Author: Rajakavitha1

docs/guides/security/basics/using-fail2ban-to-secure-your-server-a-tutorial/index.md

@@ -483,13 +483,7 @@ The best way to understand how failregex works is to write one. Although we do n
     <HOST> - - \[(\d{2})/\w{3}/\d{4}:
     ```
 
-1.  The next sequence is a series of two-digit numbers that make up the time. Because we defined the day of the month as a two-digit number in a capture group (the parentheses), we can backreference it using `\1` (since it is the *first* capture group). Again, the colons are literals:
-
-    ```command
-    <HOST> - - \[(\d{2})/\w{3}/\d{4}:\1:\1:\1
-    ```
-
-    If you do not want to use backreferences this can also be written as:
+1.  The next sequence is a series of two-digit numbers that make up the time. Again, the colons are literals:
 
     ```command
     <HOST> - - \[\d{2}/\w{3}/\d{4}:\d{2}:\d{2}:\d{2}
@@ -617,4 +611,4 @@ CentOS 7 and Fedora additionally require two extra commands to be fully stopped
 
 ```command
 systemctl disable --now fail2ban
-```
+```