cmd/go: spurious "v1.x.y is not a tag" error when a tag's commit was previously download without the tag [1.21 backport]

[gopherbot]

@bcmills requested issue #53955 to be considered for backport to the next 1.21 minor release.

@gopherbot, please backport to Go 1.21 and 1.20. This fixes a bug that is otherwise difficult for users to understand and diagnose, and the fix is relatively uninvasive.

[bcmills]

On the other hand, this has a fairly straightforward workaround: retrying the operation causes it to succeed.

[joedian]

@matloob Can you please make a decision on this backport?