fix: uploading progress percentage

[KristinAoki]

JIRA Ticket: TNL-11308

When chunking the uploaded file was introduced, the upload progress percentage began to loop for each chunks upload. The looping of percentages is confusing to users as it seems like the upload is stuck in an infinite loop and they do not know how much the file has successfully uploaded. This PR fixes the progress bar so it updates after each chunk is uploaded.

Test

1. Export the current content of your course
2. Open the network tab in DevTools
3. Import the recently exported file
4. Progress percentage in Uploading step should only reach 100% one time even when the file is chunked multiple times (confirm number of chunks in network tab)

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (782fadd) 89.56% compared to head (a8bcddb) 89.56%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
src/import-page/data/thunks.js	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #763   +/-   ##
=======================================
  Coverage   89.56%   89.56%           
=======================================
  Files         495      495           
  Lines        8069     8072    +3     
  Branches     1697     1698    +1     
=======================================
+ Hits         7227     7230    +3     
  Misses        815      815           
  Partials       27       27           

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[jesperhodge]

I checked this manually and this works. However, if this was bothersome enough that people actually filed a bug for it, then it also warrants us writing a test to ensure that we don't break it in the future.

Let's just add a test to the specific thing that was changed here until the codecov/patch pipeline passes. I'll approve the PR though.

Generally the api.js file seems barely test covered, and we should extend the test coverage here quite a bit anyway. Since it's mostly adding tests to existing code, I would suggest that we create a followup issue for this.