github issue template: capitalize given/when/then
github issue template: capitalize given/when/then

They're already bold, so the all-caps isn't necessary and hurts my
overly sensitive brain :-)

HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence,HackBrexit/MinistersUnderTheInfluence