housekeeping: fix indentation
housekeeping: fix indentation

Fix indentation on `ngx_http_pagespeed_writer` and
`ngx_http_pagespeed_write_helper`.

0x0mar/ngx_pagespeed,0x0mar/ngx_pagespeed,digideskio/ngx_pagespeed,pagespeed/ngx_pagespeed,wanrui/ngx_pagespeed,digideskio/ngx_pagespeed,wanrui/ngx_pagespeed,pagespeed/ngx_pagespeed