[baloo-widgets] Display releaseYear w/o decimal grouping

Summary: Display release year as e.g. "2010" instead of "2.010"

Test Plan: Visual inspection

Reviewers: #frameworks, #dolphin, broulik

Reviewed By: broulik

Subscribers: elvisangelaccio, ngraham

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D9887