risc-v/rv-virt: Remove SCANFTEST from rv-virt:citest

[lupyuen]

Summary

CONFIG_TESTING_SCANFTEST is no longer needed in rv-virt:citest defconfig because of apache/nuttx-apps#2914

This PR excludes CONFIG_TESTING_SCANFTEST from rv-virt:citest so that CI Job risc-v-05 will complete successfully.

Impact

With this PR, CI Job risc-v-05 will complete successfully.

Testing

Before this PR: CI Job risc-v-05 fails at CONFIG_TESTING_SCANFTEST
https://github.com/apache/nuttx/actions/runs/12329209626/job/34829161894?pr=15187#step:7:1268

  Normalize rv-virt/citest
< CONFIG_TESTING_SCANFTEST=y
Changes not staged for commit:
	modified:   boards/risc-v/qemu-rv/rv-virt/configs/citest/defconfig

After this PR: CI Job risc-v-05 completes successfully in Docker:
https://gist.github.com/lupyuen/47ad49c65d12f299451a2dcb7ef90452

sudo docker run \
  -it \
  ghcr.io/apache/nuttx/apache-nuttx-ci-linux:latest \
  /bin/bash
cd
git clone https://github.com/lupyuen2/wip-nuttx nuttx --branch scanftest
git clone https://github.com/apache/nuttx-apps apps
pushd nuttx ; echo NuttX Source: https://github.com/apache/nuttx/tree/$(git rev-parse HEAD) ; popd
pushd apps  ; echo NuttX Apps: https://github.com/apache/nuttx-apps/tree/$(git rev-parse HEAD) ; popd
cd nuttx/tools/ci
./cibuild.sh -c -A -N -R testlist/risc-v-05.dat 

Configuration/Tool: rv-virt/citest
Normalize rv-virt/citest
[no errors]