Remove xblockutils package

[farhan]

Parent ticket: openedx/axim-engineering#915

This repository is using the xblock-utils package which has been deprecated and migrated to within the xblock package.

In this ticket, we will:

Tasks

Beta Give feedback

1. Make sure the repository is using xblock version 1.8.1 or above. Upgrade the version if required, preferably via the make upgrade command.
2. Remove the xblock-utils package
3. Find and replace all the xblockutils.* imports with xblock.utils.*
4. Make sure all the test cases are passing
5. Test the xblock

[feanil]

This was fixed in #434 which has been merged.