Update packages and linting

[zorkow]

• Updates all packages to latest version except for typescript
• Fixes all linting errors of the form no-useless-assignment. These generally make things clearer. The only exceptions are in Wrappers/mo.ts and Wrappers/mmultiscripts.ts where it makes things slightly uglier.

[dpvc]

One issue with an incorrect comment, but otherwise ok.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.92%. Comparing base (45dd68b) to head (90c6648).
⚠️ Report is 19 commits behind head on develop.

Files with missing lines	Patch %	Lines
ts/output/common/Wrappers/mmultiscripts.ts	0.00%	2 Missing ⚠️
ts/output/common/Wrappers/mo.ts	0.00%	2 Missing ⚠️
ts/core/MmlTree/MmlNodes/mo.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1542      +/-   ##
===========================================
- Coverage    86.93%   86.92%   -0.02%     
===========================================
  Files          388      390       +2     
  Lines        87571    87857     +286     
  Branches      3290     4983    +1693     
===========================================
+ Hits         76129    76368     +239     
- Misses       11442    11489      +47     

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