Add a working poetry version to .tool-versions

This stops `asdf` from throwing an *incredibly* obnoxious error the first time you try to run the `poetry` binary it's literally just installed for you:

```
 $ poetry --help
No version is set for command poetry
Consider adding one of the following versions in your config file at /Users/alex/src/repository-template/.tool-versions
poetry 1.6.1
```

.tool-versions

@@ -1,5 +1,6 @@
 nodejs 18.17.1 # Always check AWS and Azure runtime support
 python 3.11.4 # Always check AWS and Azure runtime support
+poetry 1.6.1
 terraform 1.5.6
 pre-commit 3.3.3