Remove default webpacker path to linked_dirs

[taketo1113]

Summary

Remove default webpacker path to linked_dirs.
Webpacker deprecated from rails v7.0.

https://github.com/rails/webpacker

Short checklist

• Did you run bundle exec rubocop -a to fix linter issues?
• If relevant, did you create a test?
• Did you confirm that the RSpec tests pass?

[mattbrictson]

Thanks for the contribution! Some thoughts:

• Webpacker has been deprecated, but it is still widely used by existing Rails apps. However, this change only affects new apps (i.e. when cap install is run), so the potential negative impact to existing Capistrano-enabled Rails projects is minimal.
• Webpack support for Rails lives on in a gem called shakapacker. However, this gem uses a different cache location (tmp/shakapacker¹), so it will not be affected by this change.

Overall I think this is a good removal of cruft and should be safe. @leehambley @will-in-wi any objections?

Footnotes

1. https://github.com/shakacode/shakapacker/blob/732ba010e6b54697875a19ad01e4975941a02c3f/lib/install/config/shakapacker.yml#L24 ↩

[leehambley]

Looks great, thanks for taking the initiative everyone 🙌