Port Seq.ungap call to biopython 1.80. (#101)
Since Biopython 1.80, the call to Seq.ungap(gap) is deprecated and
replaced by Seq.replace(gap, ‘’).  Sticking to ungap is currently
causing Debian bug #1066772.  This change allows running ungap
workloads with Biopython versions 1.80 and newer.
Signed-off-by: Étienne Mollier emollier@debian.org