UPGRADING: Rename PDO driver-specific class names

Follow-up to phpGH-14069.

Signed-off-by: Ayesh Karunaratne <[email protected]>

Author: Ayesh

UPGRADING

@@ -259,22 +259,22 @@ PHP 8.4 UPGRADE NOTES
     or by invoking their constructor directly.
 
 - PDO_DBLIB:
-  . Added class PdoDbLib.
+  . Added class Pdo\DbLib.
 
 - PDO_FIREBIRD:
-  . Added class PdoFirebird.
+  . Added class Pdo\Firebird.
 
 - PDO_MYSQL:
-  . Added class PdoMysql.
+  . Added class Pdo\Mysql.
 
 - PDO_ODBC:
-  . Added class PdoOdbc.
+  . Added class Pdo\Odbc.
 
 - PDO_PGSQL:
-  . Added class PdoPgsql.
+  . Added class Pdo\Pgsql.
 
 - PDO_SQLITE:
-  . Added class PdoSqlite.
+  . Added class Pdo\Sqlite.
 
 - POSIX:
   . Added constant POSIX_SC_CHILD_MAX