Bump CommunityToolkit.Mvvm from 8.3.2 to 8.4.0

Bumps [CommunityToolkit.Mvvm](https://github.com/CommunityToolkit/dotnet) from 8.3.2 to 8.4.0.
- [Release notes](https://github.com/CommunityToolkit/dotnet/releases)
- [Commits](CommunityToolkit/dotnet@v8.3.2...v8.4.0)

---
updated-dependencies:
- dependency-name: CommunityToolkit.Mvvm
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Flow.Launcher/Flow.Launcher.csproj

@@ -83,7 +83,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="CommunityToolkit.Mvvm" Version="8.3.2" />
+    <PackageReference Include="CommunityToolkit.Mvvm" Version="8.4.0" />
     <PackageReference Include="Fody" Version="6.5.4">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>