The Differ no longer catches CompatibilityErrors

This was introduced in
https://github.com/rspec/rspec-expectations/pull/220/files#diff-9533f5f156a38a3307ecfc610d2282d7R47

but is no longer raised either by the the current test code, the
original test code
      @expected="Tu avec carté {count} itém has".encode('UTF-16LE')
      @Actual="Tu avec carte {count} item has".encode('UTF-16LE')
or any other variations I've tried

Since I'm moving all the encoding logic into EncodedString, and this
doesn't appear to do anything any more, I am proposing to remove it.

Next commits will also move over #pick_encoding

Conflicts:
	spec/rspec/support/differ_spec.rb

lib/rspec/support/differ.rb

@@ -51,8 +51,6 @@ def diff_as_string(actual, expected)
         finalize_output(output, hunks.last.diff(format_type).to_s) if hunks.last
 
         color_diff output
-      rescue Encoding::CompatibilityError
-        handle_encoding_errors
       end
       # rubocop:enable MethodLength
 
@@ -202,17 +200,6 @@ def pick_encoding(source_a, source_b)
         def pick_encoding(_source_a, _source_b)
         end
       end
-
-      def handle_encoding_errors
-        if @actual.source_encoding != @expected.source_encoding
-          "Could not produce a diff because the encoding of the actual string " \
-          "(#{@actual.source_encoding}) differs from the encoding of the expected " \
-          "string (#{@expected.source_encoding})"
-        else
-          "Could not produce a diff because of the encoding of the string " \
-          "(#{@expected.source_encoding})"
-        end
-      end
     end
     # rubocop:enable ClassLength
   end