ics: use http:, not https:, for pyconuk.org links
ics: use http:, not https:, for pyconuk.org links

Not only did I have a missing slash in the initial version, apparently I
didn't even re-test the links after adding it...

PyconUK/2015.pyconuk.org,wjt/pyconuk.org,BjarniRunar/pyconuk.org,PyconUK/pyconuk.org,PyconUK/2015.pyconuk.org,sixty-north/pyconuk.org,wjt/pyconuk.org,zeth/pyconuk.org,Avaren/pyconuk.org,tomviner/pyconuk.org,tomviner/pyconuk.org,grimpunch/pyconuk.org,jneves/pyconuk.org,jamesbroadhead/pyconuk.org,evildmp/pyconuk.org,PyconUK/pyconuk.org,evildmp/pyconuk.org,evildmp/pyconuk.org,jneves/pyconuk.org,sixty-north/pyconuk.org,Avaren/pyconuk.org,jamesbroadhead/pyconuk.org,BjarniRunar/pyconuk.org,BjarniRunar/pyconuk.org,jneves/pyconuk.org,zeth/pyconuk.org,grimpunch/pyconuk.org,PyconUK/2015.pyconuk.org,Avaren/pyconuk.org,zeth/pyconuk.org,moreati/pyconuk.org,moreati/pyconuk.org,tomviner/pyconuk.org,moreati/pyconuk.org,PyconUK/pyconuk.org,grimpunch/pyconuk.org,sixty-north/pyconuk.org,wjt/pyconuk.org,jamesbroadhead/pyconuk.org