iwyu: remove unneeded includes in sc, sd, sw

Remove only include for files where iwyu does not suggest any
includes to add.

Change-Id: I58f3e956485ce058750c2635db9633736708d7f0
Reviewed-on: https://gerrit.libreoffice.org/12342
Reviewed-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>
Tested-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>