Fix issue that causes learners to skip every other question in an exercise

[rtibbles]

Summary

• During testing of Studio hotfixes, an issue became apparent that Kolibri was only displaying every other question of an exercise when the questions were not randomized
• It became apparent that this was caused by the totalattempts being incremented twice on the client side when an attempt was submitted, which is then used to determine the next question to display - which was then skipping every other question, as it was going up by 2 at a time instead of 1.

Reviewer guidance

• Verify that questions are now displayed in proper order

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[radinamatic]

Yep, finally seeing the same order of questions in Kolibri exercise as it is on Studio, when the Randomize order... option is unchecked! 💯

cc @pcenov to confirm the fix so we can approve and merge for the upcoming patch.

[radinamatic]

Manual QA passes, good to go! 💯

[marcellamaki]

lgtm!