fix: update frontend version and tox.ini file

[orfeas-k]

Follow up PR to #51

• update version according to canonical/bundle-kubeflow#747
• refactor tox.ini according to canonical/oidc-authservice-rock#14 and canonical/bundle-kubeflow#763
• fix https://github.com/canonical/kfp-operators/issues/337
• add comment about command
• use placeholder instead of bundle-integration tests due to #61 (there are no charm integration tests for this charm)
• add placeholder instead of sanity tests since there are none at the moment

Note CI needs a sanity and `integration environment in order to not fail and be able to publish the produced ROCK after merging this.

Tests

ROCK can be built and unit goes to active using it, after updating its command according to ROCK. I didn't run any hands-on tests since this is really time consuming and I intend to run the bundle integration and manual tests once all kfp ROCKs are updated.

Refs #43 Fixes canonical/kfp-operators#337