Fix bioconductor tests.

It looks like a previously made assumption was incorrect.

While we're here, remove a workaround -- it seems to work now.

osv/ecosystems/bioconductor.py

@@ -61,20 +61,12 @@ def _enumerate_versions(self,
     """Helper method to enumerate versions from a specific URL."""
 
     versions = []
-    # Currently breaking on 3.19,
-    # see https://github.com/google/osv.dev/pull/1477/files#r1575458933
-    try:
-      bioc_versions.remove('3.19')
-    except ValueError:
-      pass
     for version in bioc_versions:
       response = requests.get(
           url.format(package=package, bioc_version=version),
           timeout=config.timeout)
       if response.status_code == 404:
-        # Break here as we're starting at latest and going back
-        # as packages won't disappear.
-        break
+        continue
 
       if response.status_code != 200:
         raise RuntimeError(