docs: fix grammar error (#34138)
docs: fix grammar error (#34138)

in customize-theme-variable.zh-CN.md
ant-design/ant-design,icaife/ant-design,elevensky/ant-design,zheeeng/ant-design,elevensky/ant-design,ant-design/ant-design,zheeeng/ant-design,ant-design/ant-design,ant-design/ant-design,zheeeng/ant-design,icaife/ant-design,icaife/ant-design,elevensky/ant-design,elevensky/ant-design,icaife/ant-design,zheeeng/ant-design