Draft: Remove EasyRdf workaround fixed in Fossology 4.2.1

The EasyRdf 0.9 workaround can be removed when upgrading from Fossology 3.9.0 to Fossology 4.2.1

Also fixes:

• the location of the fossology dockerfile in the Docker Compose configuration
• Readme: added note about building the spdxtools container requires a build-arg called GITHUB_BOT_AUTH