Fix backtrace filtering for net-ssh

Improve our filter pattern so it works for this kind of error:

SocketError: getaddrinfo: hostname nor servname provided, or not known
  /usr/local/lib/ruby/2.2/timeout.rb:74:in `timeout'
  /usr/local/lib/ruby/2.2/timeout.rb:125:in `timeout'
  /home/tj/.gem/ruby/22/gems/net-ssh-2.9.2/lib/net/ssh.rb:207:in `new'
  /home/tj/.gem/ruby/22/gems/net-ssh-2.9.2/lib/net/ssh.rb:207:in `start'

lib/producer/core/error_formatter.rb

@@ -3,8 +3,8 @@ module Producer
     class ErrorFormatter
       FILTERS = [
         /\/producer-\w+\/(?:bin|lib)\//,
-        /\/net\/ssh\//,
-        /\/net\/sftp\//
+        /\/net-ssh/,
+        /\/net-sftp/
       ].freeze
 
       def initialize(debug: false, force_cause: [])