Update dependencies from https://github.com/dotnet/standard build 20190905.4 (dotnet#40861)

- NETStandard.Library - 2.1.0-prerelease.19455.4

Author: dotnet-maestro[bot]

eng/Version.Details.xml

@@ -38,9 +38,9 @@
       <Uri>https://github.com/dotnet/arcade</Uri>
       <Sha>00d8aa82b488f321204a0e69a81399af9df276a1</Sha>
     </Dependency>
-    <Dependency Name="NETStandard.Library" Version="2.1.0-prerelease.19455.3">
+    <Dependency Name="NETStandard.Library" Version="2.1.0-prerelease.19455.4">
       <Uri>https://github.com/dotnet/standard</Uri>
-      <Sha>209c43e7f6232e7871b6927a510c25ee7dfd5c72</Sha>
+      <Sha>c4baa9ceabeceef9d7752ed88da12c2f12c914a5</Sha>
     </Dependency>
     <Dependency Name="Microsoft.DotNet.Helix.Sdk" Version="2.0.0-beta.19454.31">
       <Uri>https://github.com/dotnet/arcade</Uri>

eng/Versions.props

@@ -52,7 +52,7 @@
     <MicrosoftNETCorePlatformsPackageVersion>3.0.0-preview9.19409.15</MicrosoftNETCorePlatformsPackageVersion>
     <runtimenativeSystemIOPortsPackageVersion>4.6.0-preview9.19409.15</runtimenativeSystemIOPortsPackageVersion>
     <!-- Standard dependencies -->
-    <NETStandardLibraryPackageVersion>2.1.0-prerelease.19455.3</NETStandardLibraryPackageVersion>
+    <NETStandardLibraryPackageVersion>2.1.0-prerelease.19455.4</NETStandardLibraryPackageVersion>
     <!-- dotnet-optimization dependencies -->
     <optimizationwindows_ntx64IBCCoreFxPackageVersion>99.99.99-master-20190905.1</optimizationwindows_ntx64IBCCoreFxPackageVersion>
     <!-- sni -->