Bump Polyfill from 1.25.0 to 1.26.0 in /src (#373)

Bumps [Polyfill](https://github.com/SimonCropp/Polyfill) from 1.25.0 to 1.26.0.
- [Commits](https://github.com/SimonCropp/Polyfill/compare/1.25.0...1.26.0)

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

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src/DiffEngine/DiffEngine.csproj

@@ -19,7 +19,7 @@
     <PackageReference Include="Fody" Version="6.8.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" Condition="$(Configuration) == 'Release'" />
     <PackageReference Include="ProjectDefaults" Version="1.0.91" PrivateAssets="all" />
-    <PackageReference Include="Polyfill" Version="1.25.0" PrivateAssets="all" />
+    <PackageReference Include="Polyfill" Version="1.26.0" PrivateAssets="all" />
     <PackageReference Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" Condition="$(TargetFramework) == 'net461'" />
     <PackageReference Include="System.Management" Version="6.0.2" />
   </ItemGroup>