fix: declare version.txt as input (#7221)
### Description
Previously we were relying on `cli/cmd/version.go` to get bumped when
the version got changed, but now we just have `version.txt`. This PR
declares that input and gets rid of the Go inputs.
This causes failures like [this
one](https://github.com/vercel/turbo/actions/runs/7747210377/job/21127375688?pr=7205#step:7:881)
where we're using an older binary due to a cache hit.
### Testing Instructions
Changing `version.txt` should now result in a cache miss
<img width="894" alt="Screenshot 2024-02-01 at 1 44 05 PM"
src="https://github.com/vercel/turbo/assets/4131117/b6996dab-e40c-4021-a7f4-01cb74313e43">
Closes TURBO-2222
