devel/eric6: Update to 20.9 release

eric 20.9 has been released. It fixes a few bugs and introduces these new features.

File Browser: changed it to react upon changed files if their contents is shown
Tasks: added separate task categories for 'Test' and 'Documentation' tasks
Mercurial Interface: removed the interface for the deprecated 'fetch' extension
VCS Interfaces: added a configuration option to disable the VCS toolbars