docs: remove EOL documentation versions 0.12 and 0.13

[killme2008]

Drop documentation for versions 0.12 and 0.13.

• Remove versioned_docs and versioned_sidebars for both versions
• Remove Chinese i18n docs and sidebar JSON for both versions
• Remove variables/variables-0.12.ts and variables/variables-0.13.ts
• Drop both entries from versions.json

Remaining versions: 1.0, 0.17, 0.16, 0.15, 0.14 (plus nightly).

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