test: expect a HTTPError like we throw now

Author: carlosmn

test/online/fetch_test.rb

@@ -48,7 +48,7 @@ def test_fetch_over_https_with_certificate_callback
     def test_fetch_over_https_with_certificate_callback_fail
       @repo.remotes.create("origin", "https://github.com/libgit2/TestGitRepository.git")
 
-      exception = assert_raises Rugged::NetworkError do
+      exception = assert_raises Rugged::HTTPError do
         @repo.fetch("origin", {
           certificate_check: lambda { |valid, host| false }
         })