test: Remove support for Node 18

[BilalQamar95]

Note: As per openedx/public-engineering#280 this can merge this after Sumac is cut.

Description

Completed upgrade to Node 20 by removing the Node 18 CI check and using .nvmrc for version to use.

See the tracking issue for further information.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.22%. Comparing base (735d978) to head (a21fff7).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1247   +/-   ##
=======================================
  Coverage   92.22%   92.22%           
=======================================
  Files        1008     1008           
  Lines       18514    18514           
  Branches     3948     3958   +10     
=======================================
  Hits        17074    17074           
+ Misses       1373     1371    -2     
- Partials       67       69    +2     

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[bradenmacdonald]

@BilalQamar95 Is this ready to merge, or are we waiting for something? And do you know why it's still showing "tests (18) Expected — Waiting for status to be reported" on the CI report here on GitHub?

[BilalQamar95]

@BilalQamar95 Is this ready to merge, or are we waiting for something?

It was recently brought to my attention that there was openedx/public-engineering#280. After the Sumac cut, PRs removing Node 18 from the CI matrix can be merged.

And do you know why it's still showing "tests (18) Expected — Waiting for status to be reported" on the CI report here on GitHub?

It is due to test that runs on Node 18. tests (18) is a required check in the CI which needs to be removed.