build(deps): bump Xamarin.Google.Android.Material in /samples (#305)

Bumps [Xamarin.Google.Android.Material](https://github.com/xamarin/AndroidX) from 1.3.0.1 to 1.4.0.
- [Release notes](https://github.com/xamarin/AndroidX/releases)
- [Commits](https://github.com/xamarin/AndroidX/commits)

---
updated-dependencies:
- dependency-name: Xamarin.Google.Android.Material
  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>

samples/LoginApp.Android/LoginApp.Android.csproj

@@ -75,7 +75,7 @@
     <PackageReference Include="ReactiveUI.AndroidX" Version="14.*" />
     <PackageReference Include="ReactiveUI.Validation" Version="2.*" />
     <PackageReference Include="ReactiveUI.Validation.AndroidX" Version="2.*" />
-    <PackageReference Include="Xamarin.Google.Android.Material" Version="1.3.0.1" />
+    <PackageReference Include="Xamarin.Google.Android.Material" Version="1.4.0" />
     <!-- We are pinning transitive deps versions coming from ReactiveUI.AndroidX.
          See: https://github.com/reactiveui/ReactiveUI.Validation/pull/216#issuecomment-783218308 -->
     <PackageReference Include="Xamarin.AndroidX.Preference" Version="1.1.1.8" />