Update GoCloud to a version that supports s3ForcePathStyle

The upgrade to GoCloud v0.39.0 switched to AWS SDK v2 and dropped
support for the `s3ForcePathStyle` query parameter in the GoCloud URL.
Even though GoCloud v0.40.0 brought `use_path_style`, the legacy
`s3ForcePathStyle` parameter no longer worked with that version. This
would cause `gitaly` to fail with an `unknown query parameter`.

https://github.com/google/go-cloud/pull/3505 adds back
`s3ForcePathStyle` as an alias for `use_path_style` to preserve
backwards compatibility. This commit bumps the version to a pseudo-ref
that supports `s3ForcePathStyle`.

Diff:
https://github.com/google/go-cloud/compare/v0.40.0..56954848c3

Relates to https://gitlab.com/gitlab-org/gitaly/-/issues/6489

Changelog: fixed