Fix an always-false check with an assertion

In validate_recommended_package_line, at this point in the function,
n_entries is always >= 1.  Coverity doesn't like us checking it for
0.

CID 1268063.

src/or/dirserv.c

@@ -3745,7 +3745,9 @@ validate_recommended_package_line(const char *line)
     cp = end_of_word + 1;
   }
 
-  return (n_entries == 0) ? 0 : 1;
+  /* If we reach this point, we have at least 1 entry. */
+  tor_assert(n_entries > 0)
+  return 1;
 }
 
 /** Release all storage used by the directory server. */