update_repo: fix remove functionality for fedora

Found that running package removement command from S3:

  ./tools/update_repo.sh -o=fedora -d=30 -b=s3://tarantool_repo/live/1.10 -r=tarantool-1.10.9.108

it searched to remove:

  Searching to remove: s3://tarantool_repo/live/1.10/fedora/30/SRPMS/Packages/tarantool-1.10.9.108-1.fedora30.src.rpm

while it had to be:

  Searching to remove: s3://tarantool_repo/live/1.10/fedora/30/SRPMS/Packages/tarantool-1.10.9.108-1.fc30.src.rpm

where 'fc30' had to be instead of 'fedora30'. This patch fixes it.