Remove worked examples from Skill objects in asset download script.

[seanlip]

Explanation

Removes worked example from Skill objects in asset download script, and updates the state schema compatibility to v57.

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".) (N/A)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

[BenHenning]

Thanks @seanlip! I'm assuming this fixes most of the issues once the backup server has updated data and other fixes. Perhaps enough?

Separately, we should also remove worked_examples from the app's proto (by replacing it with a reserved 4 line with a comment explaining what it was):

oppia-android/model/src/main/proto/topic.proto

Lines 91 to 92 in d7ef1d5

	// A list of worked examples to present to the learner.
	repeated SubtitledHtml worked_example = 4;

Fortunately the working proto API (https://github.com/oppia/oppia-proto-api/blob/introduce-proto-api-v1/org/oppia/proto/v1/structure/revision_card.proto) never added worked examples so no change is needed there.

Finally, I do expect CI to fail here but we don't need to block on that to merge.

[seanlip]

Thanks @BenHenning -- have made the changes.

Thanks @seanlip! I'm assuming this fixes most of the issues once the backup server has updated data and other fixes. Perhaps enough?

I'm not quite sure what your question means here, but we can discuss in the call.

Finally, I do expect CI to fail here but we don't need to block on that to merge.

It seems to be stalled, actually -- everything is "queued". Not sure why.