Corrects the issue we had
[here](https://github.com/paritytech/polkadot-sdk-parachain-template/pull/10),
in which `cargo build --release` worked but `cargo build --package
parachain-template-node --release` failed with missing features.

The command has been added to CI to make sure it works, but at the same
we're changing it in the readme to just `cargo build --release` for
simplification.

Labeling silent because those packages are un-published as part of the
regular release process.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>