build(deps): bump Nullable from 1.2.1 to 1.3.0 (#537)

Bumps [Nullable](https://github.com/manuelroemer/Nullable) from 1.2.1 to 1.3.0.
- [Release notes](https://github.com/manuelroemer/Nullable/releases)
- [Changelog](https://github.com/manuelroemer/Nullable/blob/master/CHANGELOG.md)
- [Commits](https://github.com/manuelroemer/Nullable/commits)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

Directory.Build.props

@@ -14,7 +14,7 @@
     <PackageReference Include="Roslynator.Analyzers" Version="3.0.0" PrivateAssets="All" />
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0" PrivateAssets="All" />
     <PackageReference Include="Microsoft.CodeAnalysis.BannedApiAnalyzers" Version="3.3.0" PrivateAssets="All" />
-    <PackageReference Include="Nullable" Version="1.2.1" PrivateAssets="All" />
+    <PackageReference Include="Nullable" Version="1.3.0" PrivateAssets="All" />
   </ItemGroup>
 
 </Project>