Remove special CDS handling in Metaspace::allocate

The following code should be unnecessary after fixing JDK-8260341 and JDK-8261480

https://github.com/openjdk/jdk/blob/837bd8930d0a010110f1318b947c036609d3aa33/src/hotspot/share/memory/metaspace.cpp#L825-L836

    if (DumpSharedSpaces) {
      // CDS dumping keeps loading classes, so if we hit an OOM we probably will keep hitting OOM.
      // We should abort to avoid generating a potentially bad archive.
      vm_exit_during_cds_dumping(err_msg("Failed allocating metaspace object type %s of size " SIZE_FORMAT ". CDS dump aborted.",
          MetaspaceObj::type_name(type), word_size * BytesPerWord),
        err_msg("Please increase MaxMetaspaceSize (currently " SIZE_FORMAT " bytes).", MaxMetaspaceSize));
    }