fix(docs): remove duplicated characters in dev_guides

[kittimzhe]

Fix 3 duplicated-character typos in docs/dev_guides:

• api_contributing_guides/new_cpp_op_cn.md: 「变量的的 Shape」→「变量的 Shape」
• docs_contributing_guides_cn.md: 分列表里多出的一个「、」
• docs_contributing_guides_cn.md: 「CI 运行的的 log」→「CI 运行的 log」

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