chore: Remove jRuby 9.1 listen usage guard (#283)

Author: keelerm84

lib/ldclient-rb/impl/integrations/file_data_source.rb

@@ -36,15 +36,7 @@ def initialize(data_store, data_source_update_sink, logger, options={})
             @paths = [ @paths ]
           end
           @auto_update = options[:auto_update]
-          if @auto_update && @@have_listen && !options[:force_polling] # force_polling is used only for tests
-            # We have seen unreliable behavior in the 'listen' gem in JRuby 9.1 (https://github.com/guard/listen/issues/449).
-            # Therefore, on that platform we'll fall back to file polling instead.
-            if defined?(JRUBY_VERSION) && JRUBY_VERSION.start_with?("9.1.")
-              @use_listen = false
-            else
-              @use_listen = true
-            end
-          end
+          @use_listen = @auto_update && @@have_listen && !options[:force_polling]
           @poll_interval = options[:poll_interval] || 1
           @initialized = Concurrent::AtomicBoolean.new(false)
           @ready = Concurrent::Event.new

lib/ldclient-rb/integrations/file_data.rb

@@ -93,7 +93,7 @@ module FileData
       #   Note that the default implementation of this feature is based on polling the filesystem,
       #   which may not perform well. If you install the 'listen' gem (not included by default, to
       #   avoid adding unwanted dependencies to the SDK), its native file watching mechanism will be
-      #   used instead. However, 'listen' will not be used in JRuby 9.1 due to a known instability.
+      #   used instead.
       # @option options [Float] :poll_interval  The minimum interval, in seconds, between checks for
       #   file modifications - used only if auto_update is true, and if the native file-watching
       #   mechanism from 'listen' is not being used. The default value is 1 second.