fix(Validium): Remove obscure use of `VALIDIUM_MODE` env

[ilitteri]

Disclaimer ⚠️

This PR has a counterpart in the era-contracts repo. The PR in question is https://github.com/matter-labs/era-contracts/pull/225. The era-contracts submodule is pointing to said PR's branch. Before merging this PR, after it is approved and the era-contracts counterpart is merged, we need to update this PR's submodule commit.

What ❔

This PR removes the use of VALIDIUM_MODE env for the contracts side and replaces it with the passthrough of the flag to the l1-contracts deploy script.

Why ❔

zk tool is setting VALIDIUM_MODE environment variable, which is only used by a script in a different repository (era-contracts). This is a very implicit and hard to track approach.

Checklist

• [x] PR title corresponds to the body of PR (we generate changelog entries from PRs).
• [ ] Tests for the changes have been added / updated.
• [ ] Documentation comments have been added / updated.
• [ ] Code has been formatted via zk fmt and zk lint.
• [ ] Spellcheck has been run via zk spellcheck.
• [ ] Linkcheck has been run via zk linkcheck.