Update Nokogiri to v1.12.5

What does this MR do and why?

This addresses a CVE that is only relevant to JRuby users (https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md#1125--2021-09-27), but this gem is still flagged by security scanners.

• Full diff: https://my.diffend.io/gems/nokogiri/1.11.4/1.12.5

Some other dependency updates:

• ruby-magic https://my.diffend.io/gems/ruby-magic/0.4.0/0.5.3
• racc diff: https://my.diffend.io/gems/racc/1.5.2/1.6.0
• mini_portile2: https://my.diffend.io/gems/mini_portile2/2.5.0/2.6.1

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.