contracts: Remove no longer enforced limits from the `Schedule` (#3184)

When switching from the instrumented gas metering to the wasmi gas
metering we also removed all imposed limits regarding Wasm module
internals. All those things do not interact with the host and have to be
handled by wasmi. For example, Wasmi charges additional gas for
parameters to each function because as they incur some overhead.

Back then we took the opportunity to remove the dependency on the
deprecated `parity-wasm` which was used to enforce those limits.

This PR merely removes them from the `Schedule` they aren't enforced for
a while.