docs: fix incorrect description

We don't have PDO and ODBC drivers.
Some driver uses DSN to connect, but it is not a must
because CI builds it from other settings.

Author: kenjis

user_guide_src/source/database/configuration.rst

@@ -35,15 +35,15 @@ while connecting to specify a group name.
 DSN
 ---
 
-Some database drivers (such as PDO, PostgreSQL, Oracle, ODBC) might
-require a full DSN string to be provided. If that is the case, you
-should use the 'DSN' configuration setting, as if you're using the
-driver's underlying native PHP extension, like this:
+Some database drivers (such as Postgre, OCI8) requires a full DSN string to connect.
+But if you do not specify a DSN string for a driver that requires it, CodeIgniter
+will try to build it with the rest of the provided settings.
 
-.. literalinclude:: configuration/002.php
+If you specify a DSN, you should use the ``'DSN'`` configuration setting, as if
+you're using the driver's underlying native PHP extension, like this:
 
-.. note:: If you do not specify a DSN string for a driver that requires it, CodeIgniter
-    will try to build it with the rest of the provided settings.
+.. literalinclude:: configuration/002.php
+    :lines: 11-15
 
 DSN in Universal Manner
 ^^^^^^^^^^^^^^^^^^^^^^^

user_guide_src/source/database/configuration/002.php

@@ -1,13 +1,18 @@
 <?php
 
-// PDO
-$default = [
-    'DSN' => 'pgsql:host=localhost;port=5432;dbname=database_name',
+namespace Config;
+
+use CodeIgniter\Database\Config;
+
+class Database extends Config
+{
     // ...
-];
 
-// Oracle
-$default = [
-    'DSN' => '//localhost/XE',
+    // OCI8
+    public array $default = [
+        'DSN' => '//localhost/XE',
+        // ...
+    ];
+
     // ...
-];
+}