Bump NuGet.Packaging and NuGet.Protocol

Bumps NuGet.Packaging from 6.12.5 to 7.3.1
Bumps NuGet.Protocol from 6.12.5 to 7.3.1

---
updated-dependencies:
- dependency-name: NuGet.Packaging
  dependency-version: 7.3.1
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: NuGet.Protocol
  dependency-version: 7.3.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Directory.Packages.props

@@ -45,8 +45,8 @@
     <PackageVersion Include="Microsoft.SemanticKernel.Connectors.PgVector" Version="$(SemanticKernelVersion)-preview" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="10.0.202" />
     <!-- Pin to patched versions; NuGet.Protocol 6.12.5+ fixes GHSA-g4vj-cjjj-v7hg (pulled in by Microsoft.VisualStudio.Web.CodeGeneration.Design) -->
-    <PackageVersion Include="NuGet.Packaging" Version="6.12.5" />
-    <PackageVersion Include="NuGet.Protocol" Version="6.12.5" />
+    <PackageVersion Include="NuGet.Packaging" Version="7.3.1" />
+    <PackageVersion Include="NuGet.Protocol" Version="7.3.1" />
     <PackageVersion Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.23.0" />
     <PackageVersion Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="10.0.2" />
     <PackageVersion Include="Microsoft.Extensions.AI.OpenAI" Version="10.0.1-preview.1.25571.5" />