[DURACOM-429] simplify truncatable calculation

[FrancescoMolinaro]

References

Fixes #4948

Description

Fixed and simplyfied the truncatable calculation for overflow.

Instructions for Reviewers

Configure some complex html inside a truncatable or follow #4948 for instruction on how to reproduce.

List of changes in this PR:

Refactred method truncateElement in truncatable-part.component.ts

Checklist

This checklist provides a reminder of what we are going to look for when reviewing your PR. You do not need to complete this checklist prior creating your PR (draft PRs are always welcome).
However, reviewers may request that you complete any actions in this list if you have not done so. If you are unsure about an item in the checklist, don't hesitate to ask. We're here to help!

• My PR is created against the main branch of code (unless it is a backport or is fixing an issue specific to an older branch).
• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes ESLint validation using npm run lint
• My PR doesn't introduce circular dependencies (verified via npm run check-circ-deps)
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• My PR aligns with Accessibility guidelines if it makes changes to the user interface.
• My PR uses i18n (internationalization) keys instead of hardcoded English text, to allow for translations.
• My PR includes details on how to test it. I've provided clear instructions to reviewers on how to successfully test this fix or feature.
• If my PR includes new libraries/dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• If my PR fixes an issue ticket, I've linked them together.