Update NuGet from 5.2.0 to 5.11.0 (#1724)

* Update NuGet from 5.2.0 to 5.11.0

* Update NuGet for MRT

build/AzurePipelinesTemplates/WindowsAppSDK-InstallNuget-Steps.yml

@@ -1,5 +1,5 @@
 parameters:
-  nugetVersion: 5.2.0
+  nugetVersion: 5.11.0
 
 steps:
   - task: NuGetToolInstaller@0

build/build-mrt.yml

@@ -14,9 +14,9 @@ steps:
     modifyEnvironment: true
 
 - task: NuGetToolInstaller@1
-  displayName: 'Use NuGet 5.6'
+  displayName: 'Use NuGet 5.11'
   inputs:
-    versionSpec: 5.6
+    versionSpec: 5.11
   continueOnError: true
 
 # Start restoring packages for C++ projects. The C# ones will be restored by the build task

build/publish-mrt.yml

@@ -3,9 +3,9 @@ parameters:
 
 steps:
 - task: NuGetToolInstaller@1
-  displayName: 'Use NuGet 5.6'
+  displayName: 'Use NuGet 5.11'
   inputs:
-    versionSpec: 5.6
+    versionSpec: 5.11
   continueOnError: true
 
 - task: DownloadBuildArtifacts@0