Fix merge cells height calculation, and revert line-height style changes

[adrianspdev]

Context

This PR includes fixes for merge cells plugin row height calculation, problem with gap between the selected cell at the edge of the viewport and misaligned when editing a cell in the first row.

How has this been tested?

Locally

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature or improvement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Additional language file or change to the existing one (translations)

Related issue(s):

1. https://github.com/handsontable/dev-handsontable/issues/2219
2. https://github.com/handsontable/dev-handsontable/issues/2220
3. https://github.com/handsontable/dev-handsontable/issues/2208

Affected project(s):

• handsontable
• @handsontable/angular
• @handsontable/react
• @handsontable/react-wrapper
• @handsontable/vue
• @handsontable/vue3

Checklist:

• Fix for problem with gap between the selected cell at the edge of the viewport
• Fix for misaligned when editing a cell in the first row
• Fix for merge cell row height calculation

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