Remove unused codepaths from QV8SequenceWrapper

Remove unused codepaths from QV8SequenceWrapper

The object equality comparison callback does not allow an object with
a sequence resource to be equal to an object with a variant resource.
As such, the SequenceType::isEqual(QVariant) codepaths are not needed.
Also, QVariantList conversion is handled by toBasicVariant() in the
QV8Engine, and thus we don't need conversion code for this type in
the sequence wrapper.

Change-Id: I2ec599c5ad6cfdb715cd4e0aae3f0cc3bb36cfdf
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>