Fix group in twofactorauth plugins (#35638)

Author: wojsmol

plugins/twofactorauth/totp/totp.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<extension version="3.1" type="plugin" group="system" method="upgrade">
+<extension version="3.1" type="plugin" group="twofactorauth" method="upgrade">
 	<name>plg_twofactorauth_totp</name>
 	<author>Joomla! Project</author>
 	<creationDate>August 2013</creationDate>

plugins/twofactorauth/yubikey/yubikey.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<extension version="3.1" type="plugin" group="system" method="upgrade">
+<extension version="3.1" type="plugin" group="twofactorauth" method="upgrade">
 	<name>plg_twofactorauth_yubikey</name>
 	<author>Joomla! Project</author>
 	<creationDate>September 2013</creationDate>