Python: Update pyproject.toml to version 0.3.13.dev (#2859)

Update pip version in preparation for next package release

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### Contribution Checklist

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- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
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raises no violations
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- [ ] I didn't break anyone 😄

python/pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "semantic-kernel"
-version = "0.3.12.dev"
+version = "0.3.13.dev"
 description = ""
 authors = ["Microsoft <SK-Support@microsoft.com>"]
 readme = "pip/README.md"