PR #9564 breaks manifest update on Windows

[Hexcles]

PR #9564 (which is a fix for #7142) breaks manifest update on Windows because the change violates Windows' restrictions on parallel file access.

There are two issues in this line https://github.com/w3c/web-platform-tests/pull/9564/files#diff-2a239eec150d25cf7486394513fb1e63R242:

1. The temp file is moved before it's closed, which can be easily fixed.
2. The much harder problem is the manifest itself. manifest is a file-like object, which means it's already opened somewhere else, so overwriting the file (with a new file handler) will fail on Windows. And we can't simply close manifest here because it'd invalidate the handler, causing other failures.

My proposal is to revert #9564 (which means reopen #7142 ), because currently all wpt commands are unusable on Windows while #7142 is just an edge case.