fix: snippets/csharp/Microsoft.Extensions.DependencyModel/DependencyContext/Overview/DependencyContextSnippets.csproj to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DOTNET-SYSTEMTEXTJSON-8168848

Author: snyk-bot

snippets/csharp/Microsoft.Extensions.DependencyModel/DependencyContext/Overview/DependencyContextSnippets.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.DependencyModel" Version="6.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyModel" Version="7.0.0" />
   </ItemGroup>
 
 </Project>