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

`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.

Author: lupyuen

boards/risc-v/qemu-rv/rv-virt/configs/citest/defconfig

@@ -134,7 +134,6 @@ CONFIG_TESTING_LTP=y
 CONFIG_TESTING_MM=y
 CONFIG_TESTING_OPEN_MEMSTREAM=y
 CONFIG_TESTING_OSTEST=y
-CONFIG_TESTING_SCANFTEST=y
 CONFIG_TESTS_TESTSUITES=y
 CONFIG_TLS_NCLEANUP=4
 CONFIG_TLS_NELEM=8