Update mysql2 documentation in Connecting to a Database guide

Just state the options are passed to Mysql2::Client.new, instead
of trying to compare the options to the mysql adapter.

doc/opening_databases.rdoc

@@ -269,12 +269,8 @@ The following additional options are supported:
 === mysql2
 
 This is a newer MySQL adapter that does typecasting in C, so it is often faster than the
-mysql adapter.  Supports the same additional options as the mysql adapter, except for :compress, and uses
-:timeout instead of :read_timeout and :connect_timeout.
-
-The following additional options are supported:
-
-:flags :: Override the flags to use for the connection (e.g. ::Mysql2::Client::MULTI_STATEMENTS)
+mysql adapter.  The options given are passed to Mysql2::Client.new, see the mysql2 documentation
+for details on what options are supported.
 
 === odbc