Add missing step to docs

[simonhamp]

What does this PR do?

Updates install on Windows docs

Checklist before merging

If your PR involves the changes mentioned below and completed the action, please tick the corresponding option.
If a modification is not involved, please skip it directly.

• If it's an extension or dependency update, make sure adding related extensions in src/global/test-extensions.php.
• If you changed the behavior of static-php-cli, update docs in ./docs/.
• If you updated config/xxx.json content, run bin/spc dev:sort-config xxx.