Riscv: Bump Ubuntu version to 23.10

Test: QEMU boots
Change-Id: I397f9d82a09fbcc8d7e40f23dc1cec1fc48738d4
diff --git a/tools/buildbot-utils.sh b/tools/buildbot-utils.sh
index 70fa01a..1cdd275 100755
--- a/tools/buildbot-utils.sh
+++ b/tools/buildbot-utils.sh
@@ -87,7 +87,7 @@
   export RSYNC_RSH="ssh -i ~/.ssh/ubuntu -p $ART_TEST_SSH_PORT -o StrictHostKeyChecking=no" # don't prefix with "ART_", rsync expects this name
 
   if [[ "$TARGET_ARCH" =~ ^(arm64|riscv64)$ ]]; then
-    export ART_TEST_VM_IMG="ubuntu-22.04-server-cloudimg-$TARGET_ARCH.img"
+    export ART_TEST_VM_IMG="ubuntu-23.10-server-cloudimg-$TARGET_ARCH.img"
     export ART_TEST_VM_DIR="$ANDROID_BUILD_TOP/vm/$TARGET_ARCH"
     export ART_TEST_VM="$ART_TEST_VM_DIR/$ART_TEST_VM_IMG"
   else