fix another statement about hbond length constraints

Author: j-wags

examples/swap_amber_parameters/swap_existing_ligand_parameters.ipynb

@@ -433,7 +433,7 @@
     "\n",
     "## As a test, run some dynamics on the combined system\n",
     "\n",
-    "First, we create an OpenMM system, as we've done in other examples here. We can do this, in this case, using ParmEd's built-in `createSystem` functionality already attached to the combined `Structure`. We ask for a reasonable cutoff, constrained hydrogen bonds (but note above we used the `unconstrained` force field above; if this were going to be a production simulation we should be using the standard rather than the unconstrained force fiedl), PME, and rigid water:"
+    "First, we create an OpenMM system, as we've done in other examples here. We can do this, in this case, using ParmEd's built-in `createSystem` functionality already attached to the combined `Structure`. We ask for a reasonable cutoff, constrained hydrogen bonds (note that **this keyword argument overrides the fact that we use the `unconstrained` force field above**; the ligand (and all other molecules in the system) **will** have covalent bonds to hydrogen constrainted), PME, and rigid water:"
    ]
   },
   {
@@ -494,18 +494,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": null,
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stderr",
-     "output_type": "stream",
-     "text": [
-      "/Users/jwagner/miniconda3/envs/off-dev/lib/python3.7/site-packages/parmed/amber/netcdffiles.py:409: UserWarning: Could not find netCDF4 module. Falling back on scipy implementation, which can significantly slow down simulations if used as a reporter\n",
-      "  warnings.warn('Could not find netCDF4 module. Falling back on '\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "simulation.context.setVelocitiesToTemperature(300*unit.kelvin)\n",
     "simulation.step(1000)"