lib/ostruct.rb: Revert "To use RuntimeError instead of FrozenError for old ruby versions."
This reverts commit 4cd1fc8b3559353069860eee90b1b5bade013917.
lib/ostruct.rb: Revert "To use RuntimeError instead of FrozenError for old ruby versions."
This reverts commit 4cd1fc8b3559353069860eee90b1b5bade013917.