fix docker build by forcing older version of public_suffix

[gmenuel]

Similar to a PR I've done on puppetserver puppetlabs/puppetserver#2670

Currently docker build fail with the following error:

#12 41.61 	The last version of public_suffix (< 6.0, >= 2.0.2) to support your Ruby & RubyGems was 4.0.7. Try installing it with `gem install public_suffix -v 4.0.7` and then running the current command again

This PR fix this by forcing the public_suffix ruby gem to 4.0.7

[puppetlabs-jenkins]

Can one of the admins verify this patch?

[mwaggett]

hey @gmenuel, thanks again for this! For posterity, I'm making the same comment I did on the corresponding puppetserver PR:

Unfortunately, it has been decided that we will no longer be maintaining docker images for Puppet's projects. If you have tested this change and are satisfied that it solves your problem, I am happy to merge this pull request, but please be aware that we at Puppet will not be doing any additional testing of this change and we will not be fixing any bugs that may arise as a result of this, or any other changes.

If you would still like me to merge this, let me know! Otherwise, this PR will be closed in a few weeks.

[CLAassistant]

All committers have signed the CLA.