MIME type correction for .ods files in src/gdrivehelper.cpp

Summary:
KIO-GDrive appears to assign the mime type "application/x-vnd.oasis.opendocument.spreadsheet"
to .ods files in src/gdrivehelper.cpp.
However, the correct mime type is "application/vnd.oasis.opendocument.spreadsheet".

References:
https://wiki.documentfoundation.org/Faq/General/036
https://en.wikipedia.org/wiki/OpenDocument_technical_specification#Documents

BUG: 388598
FIXED-IN: 1.2.2

Test Plan:

1. Try to open a .ods file through an unpatched KIO-GDrive and notice how
   you'll receive a Choose Application prompt from Dolphin.
   This is a result of the fact that "application/x-vnd.oasis.opendocument.spreadsheet" is an unknown MIME type.

2. Repeat the test described in 1 with the patched KIO-GDrive,
   and notice how (for example) LibreOffice Calc immediately opens the file
   without going through Dolphin's Choose Application prompt first.

Differential Revision: https://phabricator.kde.org/D9706