Bump System.Memory from 4.5.4 to 4.5.5 (#620)

Bumps [System.Memory](https://github.com/dotnet/corefx) from 4.5.4 to 4.5.5.
- [Release notes](https://github.com/dotnet/corefx/releases)
- [Commits](https://github.com/dotnet/corefx/commits)

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

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

src/WinUsb/WinUsb.csproj

@@ -8,7 +8,7 @@
     <ProjectReference Include="..\Kernel32\Kernel32.csproj" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="System.Memory" Version="4.5.4" />
+    <PackageReference Include="System.Memory" Version="4.5.5" />
     <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
   </ItemGroup>
 </Project>

src/Windows.Core/Windows.Core.csproj

@@ -5,6 +5,6 @@
     <Description>P/Invoke types for common Windows APIs.</Description>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="System.Memory" Version="4.5.4" />
+    <PackageReference Include="System.Memory" Version="4.5.5" />
   </ItemGroup>
 </Project>