cannot upgrade fedora 27 -> 28 due to firefox 56 needing hunspell

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[root@fedora]~amir# dnf system-upgrade download --refresh --releasever=28

Before you continue ensure that your system is fully upgraded by running "dnf --refresh upgrade". Do you want to continue [y/N]: y

Last metadata expiration check: 0:00:00 ago on Sun 03 Jun 2018 19:14:45 IDT.

Error: Problem: package firefox-56.0-5.fc26.x8664 requires libhunspell-1.5.so.0()(64bit), but none of the providers can be installed - hunspell-1.5.4-4.fc27.x8664 does not belong to a distupgrade repository - problem with installed package firefox-56.0-5.fc26.x86_64