chore(deps): bump Microsoft.OpenApi.Kiota.Builder in /python-sdk (#5678)

Bumps [Microsoft.OpenApi.Kiota.Builder](https://github.com/microsoft/kiota) from 1.20.0 to 1.21.0.
- [Release notes](https://github.com/microsoft/kiota/releases)
- [Changelog](https://github.com/microsoft/kiota/blob/main/CHANGELOG.md)
- [Commits](microsoft/kiota@v1.20.0...v1.21.0)

---
updated-dependencies:
- dependency-name: Microsoft.OpenApi.Kiota.Builder
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

python-sdk/python-sdk.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.OpenApi.Kiota.Builder" Version="1.20.0" />
+    <PackageReference Include="Microsoft.OpenApi.Kiota.Builder" Version="1.21.0" />
   </ItemGroup>
 
 </Project>