Update references to removed .extlib and correct thirdpartylibs.xml #887
Description
In PR #878 third party library simplesamlphp was moved from (hidden) directory .extlib to a composer dependency.
Unfortunately thirdpartylibs.xml and other some locations haven't been updated (see also #885).
So additionally to the suggestion of removing .extlib/simplesamlphp from thirdpartylibs.xml (like in #885 and #886), the location should be replaced by vendor/simplesamlphp and possibly the other thirdpartylib-information updated too.
There's no example in Moodle's devdocs explaining if the composer-dependency's dependencies need to be included too, but it seems likely, as their source code is present in the plugin directory.
https://moodledev.io/docs/4.5/apis/commonfiles#thirdpartylibsxml