I think you need to boot into your system in rescue/recovery mode using Fedora installation media. Once you are in chroot shell, do this:
0. Before everything, backup.
1. Determine which partition has the current /boot mountpoint.
Let's just assume that /boot is mounted from, say, /dev/sda1
partition. Change this according to your own output.
2. Unmount the existing /boot partition.
# umount /boot
3. Mount partition temporarily to other mount point
# mount /dev/sda1
4. Copy the content of "/boot partition" to "/boot directory".
# cp -a /mnt/* /boot
5. Tell the system not to automatically mount from /dev/sda1 partition to /boot mountpoint again.
# perl -pi.bak -e 's/(^.+\s+\/boot\s+)/#$1/g' /etc/fstab
Actually, it is easier to open /etc/fstab in vi (or using your favorite editor) and add a "#' to comment out the line that have "/boot" keyword.
6. Fix the grub2 menu entries. This will modify the grub.cfg in the new "/boot directory", which is exactly what we want.
# grub2-mkconfig -o /boot/grub2/grub.cfg
7. Reboot. If everything goes well, you should now boot from /boot directory. Double check that by using lsblk command again. You should not see /boot mountpoint anymore.
Note that we have not reclaimed the space of the "old" /boot partition yet. So, if the above does not work for you, you can still revert back easily. Good luck.