Remove remaining references to dropped db engines (#8767)

INSTALL

@@ -13,7 +13,7 @@ REQUIREMENTS
 * .htaccess support allowing overrides for DirectoryIndex
 * PHP Version 7.3 or greater including:
    - PCRE, DOM, JSON, Session, Sockets, OpenSSL, Mbstring, Filter, Ctype, Intl (required)
-   - PHP PDO with driver for either MySQL, PostgreSQL, SQL Server, Oracle or SQLite (required)
+   - PHP PDO with driver for either MySQL, PostgreSQL or SQLite (required)
    - Iconv, Zip, Fileinfo, Exif (recommended)
    - LDAP for LDAP addressbook support (optional)
    - GD, Imagick, XMLWriter (optional: thumbnails generation, QR-code)

config/config.inc.php.sample

@@ -21,7 +21,7 @@ $config = [];
 
 // Database connection string (DSN) for read+write operations
 // Format (compatible with PEAR MDB2): db_provider://user:password@host/database
-// Currently supported db_providers: mysql, pgsql, sqlite, mssql, sqlsrv, oracle
+// Currently supported db_providers: mysql, pgsql, sqlite
 // For examples see http://pear.php.net/manual/en/package.database.mdb2.intro-dsn.php
 // NOTE: for SQLite use absolute path (Linux): 'sqlite:////full/path/to/sqlite.db?mode=0646'
 //       or (Windows): 'sqlite:///C:/full/path/to/sqlite.db'

config/defaults.inc.php

@@ -25,7 +25,7 @@ $config = [];
 
 // Database connection string (DSN) for read+write operations
 // Format (compatible with PEAR MDB2): db_provider://user:password@host/database
-// Currently supported db_providers: mysql, pgsql, sqlite, mssql, sqlsrv, oracle
+// Currently supported db_providers: mysql, pgsql, sqlite
 // For examples see http://pear.php.net/manual/en/package.database.mdb2.intro-dsn.php
 // Note: for SQLite use absolute path (Linux): 'sqlite:////full/path/to/sqlite.db?mode=0646'
 //       or (Windows): 'sqlite:///C:/full/path/to/sqlite.db'

program/lib/Roundcube/rcube_db.php

@@ -1260,19 +1260,7 @@ class rcube_db
             if (strpos($dsn, '+') !== false) {
                 list($proto, $dsn) = explode('+', $dsn, 2);
             }
-            if (   strpos($dsn, '//') === 0
-                && strpos($dsn, '/', 2) !== false
-                && $parsed['phptype'] == 'oci8'
-            ) {
-                // Oracle's "Easy Connect" syntax:
-                // "username/password@[//]host[:port][/service_name]"
-                // e.g. "scott/tiger@//mymachine:1521/oracle"
-                $proto_opts = $dsn;
-                $pos = strrpos($proto_opts, '/');
-                $dsn = substr($proto_opts, $pos + 1);
-                $proto_opts = substr($proto_opts, 0, $pos);
-            }
-            else if (strpos($dsn, '/') !== false) {
+            if (strpos($dsn, '/') !== false) {
                 list($proto_opts, $dsn) = explode('/', $dsn, 2);
             }
             else {