`main` download fails to install

Unzipping the `main` code and trying to install from that package fails with the following error:

```
Error: cbt.go:41:2: missing go.sum entry for module providing package cloud.google.com/go/bigtable (imported by cloud.google.com/go/cbt); to add:
go get cloud.google.com/go/cbt
```

It seems like a dependency got updated in `go.mod` but not in `go.sum`?

#### Steps to reproduce

```
curl -LO https://github.com/googleapis/cloud-bigtable-cbt-cli/archive/refs/heads/main.zip
unzip main.zip
cd cloud-bigtable-cbt-cli-main && go build .
```