The AppLauncher has a bug where it fails to fact the `app.folder` is
pointing to a directory higher than it should be. This leads to a file
not being found in the `_get_version` call from `omni.isaac.version`
module.

Updated app.folder to point to `"${exe-path}/"` instead of
`"${exe-path}/../"` in the following files:

- orbit/source/apps/orbit.python.headless.kit
- orbit/source/apps/orbit.python.headless.multicam.kit
- orbit/source/apps/orbit.python.kit

Fixes #339

- Bug fix (non-breaking change which fixes an issue)

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./orbit.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have run all the tests with `./orbit.sh --test` and they pass
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there