Only report conflicting dependencies when update is not possible

[deivid-rodriguez]

I extracted this commit from #5221, because it's also useful for me to (fix) #4867.

If I understand correctly, both rubygems/rubygems#5520 and #5221 are fixing the same issue but for different ecosystems, and we both run into the same issue where the dependency is properly updated but bin/dry-run.rb still reports conflicts.

[Nishnha]

Hey @deivid-rodriguez,

Thanks for your work on rubygems/rubygems#5520!

It should make a big impact on the Ruby PRs Dependabot can open! Once it lands I think we will also need to modify the bundler ConflictingDependencyResolver so it no longer flags locked parent dependencies as conflicting.

And yes, your work is similar to what we are doing with npm in #5221--we are leverage Arborist and npm audit fix to identify and update conflicting dependencies.

We had closed out #5221 in favor of #5239 so our PR was more up-to-date. The new PR contains the same commits, and it should be shipped in the next few weeks.

I think we will also need to apply this PR's patch to our internal Updater system for it to work in production--the dry-run.rb script essentially emulates that system for local testing.

[mctofu]

This would be fine to pull in early. It's purely cosmetic as the message doesn't prevent the update from happening.

@Nishnha I've already checked our internal updater and it already has this behavior of only reporting conflicts when the update fails.