Fix Excel Report exporter
In the server, when we generate an 'xlsxReport', it appears to work, but the resulting seems to be corrupted. When you open the resulting Excel file, it complains:

If you say yes, the result seem to be okay. Not sure what is going on.
However, the 'xlsx' export works without problems.
- See Stock > Stock Lots > Menu > Download as Excel
To reproduce the problem:
- Stock > Articles in Stock
- Verify that the export type is 'xlsxReport' (line 312 client/src/modules/stock/inventories/registry.js)
- download: Stock > Articles in Stock > Menu > Download as Excel
- Open the downloaded file and see the error message
Yeah, this is because the XLS export isn't actually an XLS export - it is an HTML file renamed to XLSX. We probably should figure out something better on the long run.
One issues is that the xlsx library we use doesn't support styling cells - I believe it is a paid feature. excel4node does, but it doesn't appear to be maintained anymore. It would be worth us reflecting on it and choosing a single library for our exports that supports all our needs.
See related Issue https://github.com/IMA-WorldHealth/bhima/issues/6342