parachain-template-node: add properties for dev chain-spec (#6560)

# Description

Reused as before the `properties` variable when defining a development
chain spec for parachain-template-node.

## Integration

N/A

## Review Notes

One line change, pretty self explanatory (it got lost within the history
of changes over the parachain-template-node/chain_spec.rs file). To be
honest, not really sure how useful it is, but I had the choice of
removing the `properties` var or reuse it as before, and I went with the
latter.

Signed-off-by: Iulian Barbu <[email protected]>