build(deps): bump FodyHelpers from 6.3.0 to 6.4.0 in /src (#2705)

Bumps [FodyHelpers](https://github.com/Fody/Fody) from 6.3.0 to 6.4.0.
- [Release notes](https://github.com/Fody/Fody/releases)
- [Commits](https://github.com/Fody/Fody/commits/6.4.0)

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

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

Author: dependabot[bot]

src/ReactiveUI.Fody/ReactiveUI.Fody.csproj

@@ -10,6 +10,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FodyHelpers" Version="6.3.0" />
+    <PackageReference Include="FodyHelpers" Version="6.4.0" />
   </ItemGroup>
 </Project>