Fix nokogiri<=1.11.0.rc4 vulnerability

Run "bundle update" and upgrade most ruby gems. This should fix a
warning from GH because of a vulnerable nokogiri version.

https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-vr8q-g5c7-m54m



Signed-off-by: Fabio Utzig <fabio.utzig@nordicsemi.no>