define unit test more stringent

this is possible due to more accurate parametrization coming from
commit 8bfdd696

loop/tests/test_sidechain_construction.cc

@@ -88,8 +88,7 @@ BOOST_AUTO_TEST_CASE(test_construct_sidechain_atoms) {
     uint end_idx = all_pos.GetLastIndex(i);
     for(uint j = start_idx; j <= end_idx; ++j){
       Real d = geom::Distance(initial_all_pos.GetPos(j), all_pos.GetPos(j));
-      //largest observed distance in TYR OH
-      BOOST_CHECK(d < 0.53);
+      BOOST_CHECK(d < 0.2);
     }
   } 
 }