Fix custom long-range correction handling in `act_openmm.py`

`do_force_settings()` has two issues around `CustomNonbondedForce` long-range corrections.

First, there was a typo/mismatched method check:

```python
elif hasattr(force, 'setLongRangeCorrection'):
force.setUseLongRangeCorrection(useDispCorr)
```
The OpenMM method is setUseLongRangeCorrection(), so the check should be:

elif hasattr(force, 'setUseLongRangeCorrection'):

Second, after fixing that typo, useDispersionCorrection = True enables long-range correction for all custom nonbonded forces, including:
```
CoulombGAUSSIAN
UseLongRangeCorrection True
```

For PME with Gaussian charges, this seems wrong because PME already handles long-range electrostatics?

Suggested fix:

```
elif hasattr(force, 'setUseLongRangeCorrection'):
force.setUseLongRangeCorrection(
useDispCorr and force.getName().startswith("VanderWaals")
)
```
so it only enables LongRangeCorrection for VanderWaals.

Also note: a .dat key like useLongRangeCorrection = True is currently ignored; only useDispersionCorrection is read.
So maybe change that as well?