Bump IsExternalInit from 1.0.2 to 1.0.3 in /Ix.NET/Source

Bumps [IsExternalInit](https://github.com/manuelroemer/IsExternalInit) from 1.0.2 to 1.0.3.
- [Release notes](https://github.com/manuelroemer/IsExternalInit/releases)
- [Changelog](https://github.com/manuelroemer/IsExternalInit/blob/master/CHANGELOG.md)
- [Commits](https://github.com/manuelroemer/IsExternalInit/commits)

---
updated-dependencies:
- dependency-name: IsExternalInit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Ix.NET/Source/System.Linq.Async.SourceGenerator/System.Linq.Async.SourceGenerator.csproj

@@ -6,6 +6,6 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" PrivateAssets="all" />
-    <PackageReference Include="IsExternalInit" Version="1.0.2" PrivateAssets="all" />
+    <PackageReference Include="IsExternalInit" Version="1.0.3" PrivateAssets="all" />
   </ItemGroup>
 </Project>