[FIX] core: remove broken time consuming checks

The two method valid valid_alternative_icon_text and valid_title_icon
represent ~13% of an install all. Rewriting them in master
with in #36373 is the main reason of the performance improvement.

Those two method logic were broken, because
`xpath += '[not(//*[' + valid_attrs_xpath + '])]'`
will actually search for valid_attrs_xpath from view root,
not from fa- node.

-since this check will only log a warning and so only impact
 bugfix, no impact on user editing views,
-since a new check is added in master with the corresponding fix in views,
-since this check doesn't really test what it is suppose to check,
-since fa accessibility is great, but not critical

->removing those check will slightly speed up build without major impact
on views quality

closes odoo/odoo#39494

Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>