Allow classes to be passed into data_sync_excluded_exceptions

This maintains parity with the Raven interface:
https://github.com/getsentry/sentry-ruby/blob/7a0cebc54c5508d379769c7af688c8218721d734/lib/raven/configuration.rb#L447

lib/govuk_app_config/govuk_error/configuration.rb

@@ -25,7 +25,7 @@ def should_capture=(closure)
     def ignore_excluded_exceptions_in_data_sync
       lambda { |error_or_event|
         data_sync_ignored_error = data_sync_excluded_exceptions.any? do |exception_to_ignore|
-          exception_to_ignore = Object.const_get(exception_to_ignore)
+          exception_to_ignore = Object.const_get(exception_to_ignore) unless exception_to_ignore.is_a?(Module)
           exception_chain = Raven::Utils::ExceptionCauseChain.exception_to_array(error_or_event)
           exception_chain.any? { |exception| exception.is_a?(exception_to_ignore) }
         rescue NameError

spec/govuk_error/configuration_spec.rb

@@ -27,12 +27,18 @@
         expect(configuration.should_capture.call(StandardError.new)).to eq(true)
       end
 
-      it "should ignore errors that have been added to data_sync_excluded_exceptions" do
+      it "should ignore errors that have been added as a string to data_sync_excluded_exceptions" do
         configuration.data_sync_excluded_exceptions << "StandardError"
 
         expect(configuration.should_capture.call(StandardError.new)).to eq(false)
       end
 
+      it "should ignore errors that have been added as a class to data_sync_excluded_exceptions" do
+        configuration.data_sync_excluded_exceptions << StandardError
+
+        expect(configuration.should_capture.call(StandardError.new)).to eq(false)
+      end
+
       it "should ignore errors whose underlying cause is an exception in data_sync_excluded_exceptions" do
         stub_const("ErrorWeCareAbout", Class.new(StandardError))
         stub_const("SomeOtherError", Class.new(StandardError))