[appveyor] remove OpenThread project due to expired certificate (#2448)
[appveyor] remove OpenThread project due to expired certificate (#2448)

Visual Studio does not like commented lines in sln files.  This PR simply
removes the commented lines.
pvanhorn/openthread,bukepo/openthread,georgecpr/openthread,librasungirl/openthread,turon/openthread,chshu/openthread,openthread/openthread,srickardti/openthread,turon/openthread,xiaom-GitHub/openthread,erja-gp/openthread,LeZhang2016/openthread,jwhui/openthread,openthread/openthread,jwhui/openthread,xiaom-GitHub/openthread,lanyuwen/openthread,pvanhorn/openthread,chshu/openthread,bukepo/openthread,mszczodrak/openthread,chshu/openthread,mszczodrak/openthread,lanyuwen/openthread,mszczodrak/openthread,mszczodrak/openthread,georgecpr/openthread,librasungirl/openthread,pvanhorn/openthread,xiaom-GitHub/openthread,chshu/openthread,librasungirl/openthread,xiaom-GitHub/openthread,mszczodrak/openthread,erja-gp/openthread,LeZhang2016/openthread,srickardti/openthread,gandreello/openthread,georgecpr/openthread,gandreello/openthread,openthread/openthread,bukepo/openthread,gandreello/openthread,gandreello/openthread,LeZhang2016/openthread,abtink/openthread,srickardti/openthread,xiaom-GitHub/openthread,mszczodrak/openthread,lanyuwen/openthread,LeZhang2016/openthread,abtink/openthread,abtink/openthread,chshu/openthread,jwhui/openthread,pvanhorn/openthread,lanyuwen/openthread,LeZhang2016/openthread,gandreello/openthread,xiaom-GitHub/openthread,LeZhang2016/openthread,gandreello/openthread,abtink/openthread,georgecpr/openthread,lanyuwen/openthread,chshu/openthread,georgecpr/openthread,lanyuwen/openthread,openthread/openthread,georgecpr/openthread,librasungirl/openthread,erja-gp/openthread,pvanhorn/openthread,turon/openthread,pvanhorn/openthread,erja-gp/openthread,erja-gp/openthread,turon/openthread,bukepo/openthread,erja-gp/openthread,srickardti/openthread,jwhui/openthread