remove md5 validation

Author: v-pratap

google/cloud/storage/internal/async/writer_connection_impl.cc

@@ -150,19 +150,11 @@ AsyncWriterConnectionImpl::Finalize(storage::WritePayload payload) {
   // Default to letting the internal hash function compute and send the checksum.
   auto action = PartialUpload::kFinalizeWithChecksum;
 
-  if (is_append || current_options.has<google::cloud::storage::UseCrc32cValueOption>() ||
-      current_options.has<google::cloud::storage::UseMD5ValueOption>()) {
+  if (is_append || current_options.has<google::cloud::storage::UseCrc32cValueOption>()) {
     if (merged.has<google::cloud::storage::UseCrc32cValueOption>()) {
       write.mutable_object_checksums()->set_crc32c(
           merged.get<google::cloud::storage::UseCrc32cValueOption>());
     }
-    if (merged.has<google::cloud::storage::UseMD5ValueOption>()) {
-      auto as_proto = storage_internal::MD5ToProto(
-          merged.get<google::cloud::storage::UseMD5ValueOption>());
-      if (as_proto) {
-        write.mutable_object_checksums()->set_md5_hash(*as_proto);
-      }
-    }
     // For appendable uploads, the internal hash function only sees the chunks uploaded
     // in this stream, not the full object. We use `kFinalize` to avoid sending this
     // partial hash, which would otherwise fail validation.