Use encoding objects for comparison instead of encoding names (#2418)

* Stop checking encoding names

Comparing the names is much less efficient than
comparing the instance directly.

It may also change in the future: https://bugs.ruby-lang.org/issues/18576

* fix one assertion

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: casperisfine

spec/integration/grid_fs_bucket_spec.rb

@@ -26,8 +26,8 @@
           actual = stream.read
         end
 
-        actual.encoding.name.should == 'ASCII-8BIT'
-        actual.should == data.dup.force_encoding('binary')
+        actual.encoding.should == Encoding::BINARY
+        actual.should == data.b
       end
     end
 
@@ -41,7 +41,7 @@
 
     context 'in UTF-8 encoding' do
       let(:data_to_write) do
-        data.encoding.name.should == 'UTF-8'
+        data.encoding.should == Encoding::UTF_8
         data.freeze
       end