Despite being part of the requirement.txt, xlrd apparently was still
optional-ish, and absent from some environments like the iotbox.
Restore this by only monkeypatching xlrd if it's actually present.
closesodoo/odoo#63045
X-original-commit: c36aa16c2cc431a1e3b3bb7047dbae4fcac13946
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>