fix(gui): remove ignored file notifications from Activity list

fix(gui): remove ignored file notifications from Activity list

These are informative notifications without any need/possibility to act
on immediately -- if a file is not synced it will be visible from the
shell integration anyway.

An eventual follow-up to this change would be to have a dialogue with an
overview of all files that were ignored (including the entry in the
ignore list that caused a specific file to be ignored).

Closes #6712

Signed-off-by: Jyrki Gadinger <nilsding@nilsding.org>