fix: lower disk size for test config

Signed-off-by: Lennard Gäher <l.gaeher@posteo.de>

Author: lgaeher

confidential-vms/linux_vm/configurations/qemu_riscv64_virt_defconfig

@@ -34,7 +34,7 @@ BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_2=n
 BR2_TARGET_ROOTFS_EXT2_3=n
 BR2_TARGET_ROOTFS_EXT2_4=y
-BR2_TARGET_ROOTFS_EXT2_SIZE="5G"
+BR2_TARGET_ROOTFS_EXT2_SIZE="1G"
 
 # Kernel
 BR2_LINUX_KERNEL=y