archive/zip: duplicate entries in FS interface [1.16 backport]

[gopherbot]

@ianlancetaylor requested issue #45345 to be considered for backport to the next 1.16 minor release.

@gopherbot Please open backport to 1.16.

This appears to be a bug in the FS interface supported by archive/zip. This interface is new in the 1.16 release.

[toothrot]

Approved. This only impacts 1.16. The new API is just broken for zip files without this change.

[gopherbot]

Change https://golang.org/cl/315249 mentions this issue: [release-branch.go1.16] archive/zip: only return directory once via io/fs.FS

[gopherbot]

Closed by merging e67a58b to release-branch.go1.16.