Reimplement modal scrolling using Bootstrap's .modal-dialog-scrollable

[jmestxr]

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:

Resolves #2362

Reimplement PR #2322

Overview of changes:

We can directly use Bootstrap's provided class .modal-dialog-scrollable (see https://getbootstrap.com/docs/5.1/components/modal/#scrolling-long-content), rather than the cumbersome way of adding custom styles (max-height and overflow-auto) previously done in PR #2322.

• Replace custom styles added previously in PR Fix unexpected closing of longer modal when clicking on scrollbar #2322 by adding .modal-dialog-scrollable to modal-content.

Anything you'd like to highlight/discuss:

Testing instructions:
Run npm test to ensure snapshot tests are updated, and

1. cd into packages/cli/test/functional/test_site and run markbind serve -d
2. navigate to test_site/testModals.html in browser and test out Trigger for modal that should overflow

Proposed commit message: (wrap lines at 72 characters)
Reimplement scrolling using .modal-dialog-scrollable

---

Checklist: ☑️

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

[codecov]

Codecov Report

Merging #2363 (905ee32) into master (ebe9b9b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2363   +/-   ##
=======================================
  Coverage   45.11%   45.11%           
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  Files         123      123           
  Lines        5165     5165           
  Branches     1086     1086           
=======================================
  Hits         2330     2330           
  Misses       2516     2516           
  Partials      319      319           

Files Changed	Coverage Δ
packages/vue-components/src/Modal.vue	100.00% <ø> (ø)

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[tlylt]

LGTM