doc: use HTTPS for LazyloadImagesBlankUrl (#1476)
doc: use HTTPS for LazyloadImagesBlankUrl (#1476)

Fixes https://github.com/pagespeed/ngx_pagespeed/issues/1358
VersoBit/mod_pagespeed,hashashin/src,pagespeed/mod_pagespeed,VersoBit/mod_pagespeed,VersoBit/mod_pagespeed,hashashin/src,hashashin/src,hashashin/src,pagespeed/mod_pagespeed,hashashin/src,pagespeed/mod_pagespeed,VersoBit/mod_pagespeed,VersoBit/mod_pagespeed,pagespeed/mod_pagespeed,hashashin/src,VersoBit/mod_pagespeed,pagespeed/mod_pagespeed,VersoBit/mod_pagespeed,pagespeed/mod_pagespeed,hashashin/src,hashashin/src,pagespeed/mod_pagespeed