[ruby/pp] Fix ::Data warning on Ruby 2.7

* It was showing on require 'pp':
  lib/pp.rb:525: warning: constant ::Data is deprecated
* Fixes ruby/pp#51

ruby/pp@4fd8f4e0bb

Author: eregon

lib/pp.rb

@@ -490,6 +490,13 @@ def pretty_print_cycle(q) # :nodoc:
   end
 end
 
+verbose, $VERBOSE = $VERBOSE, nil
+begin
+  has_data_define = defined?(Data.define)
+ensure
+  $VERBOSE = verbose
+end
+
 class Data # :nodoc:
   def pretty_print(q) # :nodoc:
     class_name = PP.mcall(self, Kernel, :class).name
@@ -522,7 +529,7 @@ def pretty_print(q) # :nodoc:
   def pretty_print_cycle(q) # :nodoc:
     q.text sprintf("#<data %s:...>", PP.mcall(self, Kernel, :class).name)
   end
-end if defined?(Data.define)
+end if has_data_define
 
 class Range # :nodoc:
   def pretty_print(q) # :nodoc:

test/test_pp.rb

@@ -172,7 +172,14 @@ def test_struct
     assert_equal("#{a.inspect}\n", PP.pp(a, ''.dup)) unless RUBY_ENGINE == "truffleruby"
   end
 
-  if defined?(Data.define)
+  verbose, $VERBOSE = $VERBOSE, nil
+  begin
+    has_data_define = defined?(Data.define)
+  ensure
+    $VERBOSE = verbose
+  end
+
+  if has_data_define
     D = Data.define(:aaa, :bbb)
     def test_data
       a = D.new("aaa", "bbb")