Remove build:ug step from CI workflow and dev docs

[tlylt]

What is the purpose of this pull request?

• Documentation update
• Bug fix
• Feature addition or enhancement
• Code maintenance
• DevOps
• Improve developer experience
• Others, please explain:

Overview of changes:
Fixes #2336

Anything you'd like to highlight/discuss:
The build:ug and build:dg will not be removed from the package.json as it may be helpful if anyone wants to build UG/DG locally without deploying.

Testing instructions:
Based on previous CI runs, should be clear that this will work.
For deploying DG example:

• https://github.com/MarkBind/markbind/actions/runs/6911332114/job/18805765021
• It does the generation and then the deployment

For deploying UG example:

• https://github.com/MarkBind/markbind/actions/runs/6138010980/job/16654520045
• Similarly for UG deployment

Proposed commit message: (wrap lines at 72 characters)
Remove build:ug step from CI workflow and dev docs

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Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

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Reviewer checklist:

Indicate the SEMVER impact of the PR:

• Major (when you make incompatible API changes)
• Minor (when you add functionality in a backward compatible manner)
• Patch (when you make backward compatible bug fixes)

At the end of the review, please label the PR with the appropriate label: r.Major, r.Minor, r.Patch.

Breaking change release note preparation (if applicable):

• To be included in the release note for any feature that is made obsolete/breaking

Give a brief explanation note about:

• what was the old feature that was made obsolete
• any replacement feature (if any), and
• how the author should modify his website to migrate from the old feature to the replacement feature (if possible).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2a12b5c) 45.66% compared to head (a4d91e2) 45.66%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2377   +/-   ##
=======================================
  Coverage   45.66%   45.66%           
=======================================
  Files         123      123           
  Lines        5199     5199           
  Branches     1097     1097           
=======================================
  Hits         2374     2374           
  Misses       2506     2506           
  Partials      319      319           

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[ong6]

LGTM