update Ruby to 2.5.8 (was 2.3.1) and nokogiri to 1.11.1

[SethTisue]

as per CVE-2020-26247

also: scala/docs.scala-lang#1909

[SethTisue]

nokogiri-1.11.1-x86_64-linux requires ruby version < 3.1.dev, >= 2.5, which is
incompatible with the current version, ruby 2.3.1p112

I'm getting a feeling of deja vu, like this isn't the first time we've tried this :-/

[sjrd]

nokogiri-1.11.1-x86_64-linux requires ruby version < 3.1.dev, >= 2.5, which is
incompatible with the current version, ruby 2.3.1p112

I'm getting a feeling of deja vu, like this isn't the first time we've tried this :-/

I think we hadn't tried to upgrade Ruby, last time we encountered the issue.