Allow Facter4 to be co-installed with PDK

[GabrielNagy]

Previously facter was locked to 2.5.1. As we're planning to increaase the minimum supported Facter version in Puppet 7 to at least 3, we should update this in PDK as well. Otherwise, projects using the latest puppet would not be able to install PDK.

[coveralls]

Coverage remained the same at 91.237% when pulling 0805268 on GabrielNagy:loosen-facter-dependency into 7e9de3b on puppetlabs:main.

[GabrielNagy]

The AppVeyor failure doesn't seem transient, will try to reproduce locally

[GabrielNagy]

I think it's transient after all.

run 1: https://ci.appveyor.com/project/puppetlabs/pdk/builds/37688744/job/w4g246po84bf1auw

Failed examples:
rspec ./spec/acceptance/convert_spec.rb:14 # pdk convert with a fresh module Command "pdk convert --template-url=https://github.com/puppetlabs/pdk-templates --force" exit_status 
rspec ./spec/acceptance/convert_spec.rb:15 # pdk convert with a fresh module Command "pdk convert --template-url=https://github.com/puppetlabs/pdk-templates --force" stderr 
rspec ./spec/acceptance/convert_spec.rb:16 # pdk convert with a fresh module Command "pdk convert --template-url=https://github.com/puppetlabs/pdk-templates --force" stdout 
rspec ./spec/acceptance/convert_spec.rb:20 # pdk convert with a fresh module File "convert_report.txt" 

run 2: https://ci.appveyor.com/project/puppetlabs/pdk/builds/37703459/job/qpxbc3e3qxseeekg

Failed examples:
rspec ./spec/acceptance/build_spec.rb:40 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" exit_status 
rspec ./spec/acceptance/build_spec.rb:41 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" stdout 
rspec ./spec/acceptance/build_spec.rb:42 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" stderr 
rspec ./spec/acceptance/build_spec.rb:43 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" stderr 
rspec ./spec/acceptance/build_spec.rb:48 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" File "pkg/testuser-build-0.1.0.tar.gz" 
rspec ./spec/acceptance/build_spec.rb:51 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" File "pkg/testuser-build-0.1.0.tar.gz" Command "minitar list -l pkg/testuser-build-0.1.0.tar.gz" exit_status 
rspec ./spec/acceptance/build_spec.rb:52 # pdk build when run inside of a module when the module has complete metadata Command "pdk build --force" File "pkg/testuser-build-0.1.0.tar.gz" Command "minitar list -l pkg/testuser-build-0.1.0.tar.gz" stdout 
rspec ./spec/acceptance/build_spec.rb:81 # pdk build when run inside of a module when the module has incomplete metadata Command "pdk build --force" exit_status 
rspec ./spec/acceptance/build_spec.rb:82 # pdk build when run inside of a module when the module has incomplete metadata Command "pdk build --force" stdout 
rspec ./spec/acceptance/build_spec.rb:83 # pdk build when run inside of a module when the module has incomplete metadata Command "pdk build --force" stderr 
rspec ./spec/acceptance/build_spec.rb:84 # pdk build when run inside of a module when the module has incomplete metadata Command "pdk build --force" stderr 
rspec ./spec/acceptance/build_spec.rb:87 # pdk build when run inside of a module when the module has incomplete metadata Command "pdk build --force" File "pkg/testuser-build-0.1.0.tar.gz" 

I managed to RDP into an appveyor worker and got yet another test to fail, so my guess is that there are rubygems connection hiccups which cause versions of gems not to be found correctly.