doc: Update README.md add YQ_VERSION

[lysliu]

Add YQ_VERSION in --build-arg

to resolve the issue below:

$ docker build -t podvm_builder \
         --build-arg CAA_SRC=https://github.com/huoqifeng/cloud-api-adaptor \
         --build-arg CAA_SRC_REF=fedora-s390x-build \
         --build-arg GO_VERSION=1.20.12 \
         --build-arg PROTOC_VERSION=3.11.4 \
         --build-arg RUST_VERSION=1.72.0 \
         --build-arg KATA_SRC=https://github.com/kata-containers/kata-containers   \
         -f Dockerfile.podvm_builder .
[+] Building 0.6s (11/20)                                                                                                                                                       docker:default
 => [internal] load .dockerignore                                                                                                                                                         0.0s
 => => transferring context: 2B                                                                                                                                                           0.0s
 => [internal] load build definition from Dockerfile.podvm_builder                                                                                                                        0.0s
 => => transferring dockerfile: 2.38kB                                                                                                                                                    0.0s
 => resolve image config for docker.io/docker/dockerfile:1.5-labs                                                                                                                         0.2s
 => CACHED docker-image://docker.io/docker/dockerfile:1.5-labs@sha256:f2e91734a84c0922ff47aa4098ab775f1dfa932430d2888dd5cad5251fafdac4                                                    0.0s
 => [internal] load metadata for docker.io/library/ubuntu:20.04                                                                                                                           0.0s
 => CACHED [ 1/11] FROM docker.io/library/ubuntu:20.04                                                                                                                                    0.0s
 => CANCELED https://github.com/protocolbuffers/protobuf/releases/download/v3.11.4/protoc-3.11.4-linux-x86_64.zip                                                                         0.2s
 => ERROR https://github.com/mikefarah/yq/releases/download//yq_linux_amd64                                                                                                               0.2s
 => https://sh.rustup.rs                                                                                                                                                                  0.1s
 => CANCELED https://dl.google.com/go/go1.20.12.linux-amd64.tar.gz                                                                                                                        0.2s
 => CANCELED [ 2/11] RUN apt-get update -y &&     apt-get install --no-install-recommends -y build-essential cloud-image-utils curl git gnupg         libdevmapper-dev libgpgme-dev lsb-  0.2s
------
 > https://github.com/mikefarah/yq/releases/download//yq_linux_amd64:
------
ERROR: failed to solve: failed to load cache key: invalid response status 404

[liudalibj]

LGTM,
Thanks @lysliu