Stop unused & broken exposure of Project object on D-Bus

Summary:
Multiple projects were exposed on the same object path
/org/kdevelop/Project, so would be conflicting.
The only method of the interface was the name() method,
which also seems to not return the expected value
(did not investigate why), also is no code known
which tries to access a /org/kdevelop/Project object

Reviewers: #kdevelop, kfunk

Reviewed By: #kdevelop, kfunk

Subscribers: kdevelop-devel

Differential Revision: https://phabricator.kde.org/D5607