Bump System.Memory from 4.5.2 to 4.5.5 in /Source/Microsoft.Gateway (#78)

Bumps [System.Memory](https://github.com/dotnet/corefx) from 4.5.2 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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Source/Microsoft.Gateway/Microsoft.InnerEye.Listener.Wix.Actions/packages.config

@@ -17,7 +17,7 @@
   <package id="Newtonsoft.Json" version="13.0.1" targetFramework="net462" />
   <package id="System.Buffers" version="4.4.0" targetFramework="net462" />
   <package id="System.ComponentModel.Annotations" version="4.7.0" targetFramework="net462" />
-  <package id="System.Memory" version="4.5.2" targetFramework="net462" />
+  <package id="System.Memory" version="4.5.5" targetFramework="net462" />
   <package id="System.Numerics.Vectors" version="4.4.0" targetFramework="net462" />
   <package id="System.Runtime.CompilerServices.Unsafe" version="4.7.1" targetFramework="net462" />
   <package id="System.Threading.Tasks.Extensions" version="4.5.4" targetFramework="net462" />