https://dhis2.atlassian.net/browse/DHIS2-16776

• disabled import/no-unused-modules for stylelint config (the module isn't used in the app, but by the d2-style lib, that's not detected by the eslint rule)
• deduplicated postcss to ensure single version, with npx yarn-deduplicate, fixes: [v8.4.19] Cannot read properties of undefined (reading 'stringify') postcss/postcss#1791
• removed d2-style.config.js so that it falls back to the default, should suffice
• ran yarn add --dev @dhis2/cli-style@latest && yarn exec d2-style add stylelint
• used yarn exec d2-style apply css to autofix all the css