Remove unit test checking NCBI Zika virus names

It seems that NCBI has changed the lineage names for Zika virus
in its neighbors table. Because they could change again in the future,
it is not good to check this in a unit test.

catch/utils/tests/test_ncbi_neighbors.py

@@ -153,15 +153,6 @@ def test_construct_neighbors_for_zika(self):
         # be many more)
         self.assertGreaterEqual(len(neighbors), 100)
 
-        # Check that most sequences have 'Zika virus' in their lineage (all
-        # should but there may be outliers so only check
-        # if at least half are)
-        num_with_zika = 0
-        for n in neighbors:
-            if 'Zika virus' in n.lineage:
-                num_with_zika += 1
-        self.assertGreaterEqual(num_with_zika, len(neighbors) / 2)
-
     # Skip this test on Travis CI because it seems to not support calls
     # to FTP servers; construct_influenza_genome_neighbors() requires an
     # FTP call