Fix `-` to `_` in Packaged applications doc (#7571)
## Summary
Small stale/typo char in docs when generating a project
```
➜ ntp -v uv-test && uv venv --python 3.12 --seed && uv init --app --package example-packaged-app
Directory /tmp/testing/uv-test created and switched to.
Using Python 3.12.4 interpreter at: /Users/coffee/.local/share/mise/installs/python/3.12/bin/python3.12
Creating virtual environment with seed packages at: .venv
+ pip==24.2
Activate with: source .venv/bin/activate.fish
Virtual environment created with Python 3.12 and activated.
Using Python 3.12.4 interpreter at: /Users/coffee/.local/share/mise/installs/python/3.12/bin/python3.12
Creating virtual environment with seed packages at: .venv
+ pip==24.2
Activate with: source .venv/bin/activate.fish
Initialized project `example-packaged-app` at `/private/tmp/testing/uv-test/example-packaged-app`
/tmp/testing/uv-test via pyenv (uv-test) on ☁ (us-east-2)
➜ tree
0 B ┌─ README.md
4096 B ├─ pyproject.toml
4096 B │ ┌─ __init__.py
4096 B │ ┌─ example_packaged_app
4096 B ├─ src
8192 B ┌─ example-packaged-app
8192 B uv-test
```
## Test Plan
Eyeballs
