[bundler/bundler] No need to activate the fileutils default gem

The version we're vendoring actually relaxed this restriction back to
2.3.0+, so we can always use the vendored version.

https://github.com/bundler/bundler/commit/d366cbfe5d

lib/bundler/vendored_fileutils.rb

@@ -1,9 +1,4 @@
 # frozen_string_literal: true
 
 module Bundler; end
-if RUBY_VERSION >= "2.4"
-  require_relative "vendor/fileutils/lib/fileutils"
-else
-  # the version we vendor is 2.4+
-  require "fileutils"
-end
+require_relative "vendor/fileutils/lib/fileutils"

spec/bundler/bundler/bundler_spec.rb

@@ -176,7 +176,7 @@ RSpec.describe Bundler do
       let(:bundler_ui) { Bundler.ui }
       it "should raise a friendly error" do
         allow(File).to receive(:exist?).and_return(true)
-        allow(bundler_fileutils).to receive(:remove_entry_secure).and_raise(ArgumentError)
+        allow(::Bundler::FileUtils).to receive(:remove_entry_secure).and_raise(ArgumentError)
         allow(File).to receive(:world_writable?).and_return(true)
         message = <<EOF
 It is a security vulnerability to allow your home directory to be world-writable, and bundler can not continue.

spec/bundler/bundler/settings_spec.rb

@@ -120,7 +120,7 @@ that would suck --ehhh=oh geez it looks like i might have broken bundler somehow
 
     context "when it's not possible to write to the file" do
       it "raises an PermissionError with explanation" do
-        expect(bundler_fileutils).to receive(:mkdir_p).with(settings.send(:local_config_file).dirname).
+        expect(::Bundler::FileUtils).to receive(:mkdir_p).with(settings.send(:local_config_file).dirname).
           and_raise(Errno::EACCES)
         expect { settings.set_local :frozen, "1" }.
           to raise_error(Bundler::PermissionError, /config/)
@@ -161,7 +161,7 @@ that would suck --ehhh=oh geez it looks like i might have broken bundler somehow
   describe "#set_global" do
     context "when it's not possible to write to the file" do
       it "raises an PermissionError with explanation" do
-        expect(bundler_fileutils).to receive(:mkdir_p).with(settings.send(:global_config_file).dirname).
+        expect(::Bundler::FileUtils).to receive(:mkdir_p).with(settings.send(:global_config_file).dirname).
           and_raise(Errno::EACCES)
         expect { settings.set_global(:frozen, "1") }.
           to raise_error(Bundler::PermissionError, %r{\.bundle/config})

spec/bundler/support/helpers.rb

@@ -593,13 +593,5 @@ module Spec
       end
       port
     end
-
-    def bundler_fileutils
-      if RUBY_VERSION >= "2.4"
-        ::Bundler::FileUtils
-      else
-        ::FileUtils
-      end
-    end
   end
 end