Cell border misaligned when loading xlsx

[vaadin-bot]

Originally by @Artur-

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1. Grab the Loan calculator file used in http://demo.vaadin.com/spreadsheet/
2. Create an empty spreadsheet
3. Populate the spreadsheet using load(InputStream) witht the Loan calculator

Expected: The same as in http://demo.vaadin.com/spreadsheet/ when clicking "Loan calculator" Actual: Cell C1 is a few pixels too wide. Clicking in the Spreadsheet corrects the problem

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Imported from https://dev.vaadin.com/ issue #18950