chore: update internal version to 3.29.0-alpha (#1755)

## Checklist

- [x] I have read the [contribution
guidelines](https://github.com/ooni/probe-cli/blob/master/CONTRIBUTING.md)
- [x] reference issue for this pull request: #1745 
- [ ] if you changed anything related to how experiments work and you
need to reflect these changes in the ooni/spec repository, please link
to the related ooni/spec pull request: <!-- add URL here -->
- [ ] if you changed code inside an experiment, make sure you bump its
version number

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## Description

We are now hacking on 3.29.0-alpha

Author: DecFox

internal/version/version.go

@@ -2,4 +2,4 @@
 package version
 
 // Version is the ooniprobe version.
-const Version = "3.28.0-alpha"
+const Version = "3.29.0-alpha"