Remove deprecated `--schema-embed` flag from documentation

> Eventually, we should update our developer documentation and remove the deprecated flag from the commands. Just not immediately since most people will still be using older versions of `cargo-concordium`.

_Originally posted by @DOBEN in https://github.com/Concordium/concordium-smart-contract-tools/pull/177#pullrequestreview-2147859988_

The `--schema-embed` flag for `cargo-concordium` is now default behavior, thus it has been deprecated. There is also now a flag that opts out of embedding called `--no-schema-embed` that may be worth mentioning in the docs? Either way, references to `--schema-embed` or `-e` should be removed from the documentation, when this feature is commonly used.