Wrong version in pyproject.toml for v1.12.0

The version set in `pyproject.toml` is still at v1.11.0 for the latest v1.12.0 release:

```
[tool.poetry]
name = "netutils"
version = "1.11.0"
description = "Common helper functions useful in network automation."
authors = ["Network to Code, LLC <opensource@networktocode.com>"]
license = "Apache-2.0"
```