chore: release v0.12.1 (#128)

## 🤖 New release
* `portgraph`: 0.12.0 -> 0.12.1

<details><summary><i><b>Changelog</b></i></summary><p>

<blockquote>

## [0.12.1](v0.12.0...v0.12.1)
- 2024-06-03

### Bug Fixes
- Link and neighbour iterators counting self-loops twice
([#132](#132))
</blockquote>


</p></details>

---
This PR was generated with
[release-plz](https://github.com/MarcoIeni/release-plz/).

Co-authored-by: hugrbot <agustin.borgna+hugrbot@quantinuum.com>

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## [0.12.1](https://github.com/CQCL/portgraph/compare/v0.12.0...v0.12.1) - 2024-06-03
+
+### Bug Fixes
+- Link and neighbour iterators counting self-loops twice ([#132](https://github.com/CQCL/portgraph/pull/132))
+
 ## 0.12.0 (2024-03-01)
 
 ### Features

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "portgraph"
-version = "0.12.0"
+version = "0.12.1"
 license = "Apache-2.0"
 
 readme = "README.md"