update container version to v47

Version v47 [1] incorporates:
- chore: Move RUST_TOOLCHAIN into build_container.sh
- chore: Refactor dialing to reduce useless hints
- riscv64: Set MIN_CORES to 4

[1] rust-vmm/rust-vmm-container#118

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

.buildkite/autogenerate_pipeline.py

@@ -60,7 +60,7 @@
 
 # This represents the version of the rust-vmm-container used
 # for running the tests.
-CONTAINER_VERSION = "v46"
+CONTAINER_VERSION = "v47"
 # The suffix suggests that the dev image with `v{N}-riscv` tag is not to be
 # confused with real `riscv64` image (it's actually a `x86_64` image with
 # `qemu-system-riscv64` installed), since AWS yet has `riscv64` machines