Add release note for v0.55.1

Author: ankur22

release notes/v0.55.1.md

@@ -0,0 +1,7 @@
+k6 `v0.55.1` is here 🎉! This release includes:
+
+- Dependency updates for `golang.org/x/net`.
+
+## Maintenance and internal improvements
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+- [#4134](https://github.com/grafana/k6/pull/4134) Updates `golang.org/x/net` which contains a fix for CVE-2024-45338.