🚨 warning: constant ::Bignum is deprecated

- Fixnum & Bignum were unified into Integer in Ruby 2.4.0

Ref: https://www.ruby-lang.org/en/news/2016/12/25/ruby-2-4-0-released/

Author: pboling

test/test_cryptutil.rb

@@ -8,14 +8,14 @@ class CryptUtilTestCase < Minitest::Test
 
   def test_rand
     # If this is not true, the rest of our test won't work
-    assert(BIG.is_a?(Bignum))
+    assert(BIG.is_a?(Integer))
 
     # It's possible that these will be small enough for fixnums, but
     # extraorindarily unlikely.
     a = OpenID::CryptUtil.rand(BIG)
     b = OpenID::CryptUtil.rand(BIG)
-    assert(a.is_a?(Bignum))
-    assert(b.is_a?(Bignum))
+    assert(a.is_a?(Integer))
+    assert(b.is_a?(Integer))
     refute_equal(a, b)
   end