Remove Internet Explorer 11 specific logic from KTextTruncator

[MisRob]

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Description

Remove logic specific to Internet Explorer 11 from KTextTruncator, including:

• The lineHeightIE prop
• The IE11 fallback from the truncate method
• Other related cleanup if identified

Impact

Starting with Kolibri 0.17, we're dropping IE11 support. Therefore, KDS no longer needs to account for IE11-specific cases. This update removes unnecessary code, making future maintenance easier.

Trade-offs

None identified.

Guidance

Target the develop branch, as this will be released as a breaking change.

Acceptance criteria

• [ ] The updated KTextTruncator is tested, for example in Kolibri, and has no regressions