Fix client linting in CI

[samfreund]

Description

When running the CI check for client linting, we were running eslint with --fix. This means we're fixing problems, then throwing an error if any problems remain. We want to throw an error if any problems exist, and not fix them, since that can't get committed.

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why
• If this PR changes behavior or adds a feature, user documentation is updated
• If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
• If this PR touches configuration, this is backwards compatible with settings back to v2025.3.2
• If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
• If this PR addresses a bug, a regression test for it is added