Add gems for net-ssh
Add gems for net-ssh

```
 DEBUG [a408bf80] 	 INFO : Loading node data from /Users/sue445/workspace/github.com/sue445/capistrano-itamae/spec/integration/cookbooks/node.yml...
 DEBUG [a408bf80] 	bundler: failed to load command: itamae (/Users/sue445/workspace/github.com/sue445/capistrano-itamae/vendor/bundle/ruby/3.0.0/bin/itamae)
 DEBUG [a408bf80] 	/Users/sue445/workspace/github.com/sue445/capistrano-itamae/vendor/bundle/ruby/3.0.0/gems/net-ssh-6.1.0/lib/net/ssh/authentication/ed25519_loader.rb:21:in `raiseUnlessLoaded': OpenSSH keys only supported if ED25519 is available (NotImplementedError)
 DEBUG [a408bf80] 	net-ssh requires the following gems for ed25519 support:
 DEBUG [a408bf80] 	 * ed25519 (>= 1.2, < 2.0)
 DEBUG [a408bf80] 	 * bcrypt_pbkdf (>= 1.0, < 2.0)
 DEBUG [a408bf80] 	See https://github.com/net-ssh/net-ssh/issues/565 for more information
 DEBUG [a408bf80] 	Gem::LoadError : "ed25519 is not part of the bundle. Add it to your Gemfile."
```

sue445/capistrano-itamae,sue445/capistrano-itamae