Update MimeTypeExtensionGuesser.php

Fixed bug for MimeType `image/x-ms-bmp`
minor #10685 Update MimeTypeExtensionGuesser.php (marktopper)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #10685).

Discussion
----------

Update MimeTypeExtensionGuesser.php

Fixed bug for MimeType `image/x-ms-bmp`

Commits
-------

be0e362 Update MimeTypeExtensionGuesser.php