Clean up obsolete file references

.gitignore

 libs/
 all.css
 *css.map
-unsupported_browser.css
 .remote-sync.json
 .sync-config.cson
 

debian/jitsi-meet-web.install

 *.ico					/usr/share/jitsi-meet/
 libs					/usr/share/jitsi-meet/
 css/all.css 			/usr/share/jitsi-meet/css/
-css/unsupported_browser.css		/usr/share/jitsi-meet/css/
 sounds					/usr/share/jitsi-meet/
 fonts					/usr/share/jitsi-meet/
 images					/usr/share/jitsi-meet/