This issue arose while researching issue #1823. The issue was not a bug;
it just required clarification to the author of how to use the software.
But, while researching, I discovered that loading html into 2
sheets of a spreadsheet has a problem if the html title tag is the same
for the 2 sheets. PhpSpreadsheet would be able to save the resulting file,
but Excel would not be able to read it properly because of the duplicate title.
The worksheet setTitle method allows for disambiguation is such a circumstance.
The html reader passed a parameter indicating "don't disambiguate", but I can't
see any harm in changing that to "disambiguate". An extremely simple fix,
with tests to back it up.
cb23cca3ec