Remove unused header var in Processor::Transproc
Remove unused header var in Processor::Transproc

After this commit is warning is gone:
    /home/travis/build/rom-rb/rom/lib/rom/processor/transproc.rb:225: warning: assigned but unused variable - header

denyago/rom,cored/rom,pvcarrera/rom,kwando/rom,endash/rom,dcarral/rom,pxlpnk/rom,rom-rb/rom,Snuff/rom,jeremyf/rom,rom-rb/rom,vrish88/rom,rom-rb/rom,dekz/rom