Use QPlatformInputContextFactoryInterface_iid instead of interface name.

An API version number was added in
qtbase/c2e0c126d8be8782201b2e4b5e47d9abe7a64df0 to prevent crashes
when changing QPA APIs. Using the macro will result in the correct
name being used depending on Qt version.

(cherry picked from commit 1663f333

)
Change-Id: I907f63146c4d64ae6ec5ccb3bd2f4cf349bf5cb1
Task-number: QTBUG-46009
Reviewed-by: Jarkko Koivikko <jarkko.koivikko@code-q.fi>