Update dependencies from https://github.com/dotnet/corefx build 20190819.5 (#26275)

- Microsoft.NETCore.Platforms - 3.0.0-preview9.19419.5
- Microsoft.Private.CoreFx.NETCoreApp - 4.6.0-preview9.19419.5

Author: dotnet-maestro[bot]

eng/Version.Details.xml

@@ -18,13 +18,13 @@
       <Uri>https://github.com/dotnet/arcade</Uri>
       <Sha>0e36c2410b72166a1b9a67142e652225e22feada</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.Private.CoreFx.NETCoreApp" Version="4.6.0-preview9.19416.11">
+    <Dependency Name="Microsoft.Private.CoreFx.NETCoreApp" Version="4.6.0-preview9.19419.5">
       <Uri>https://github.com/dotnet/corefx</Uri>
-      <Sha>b3a4cdd6cd9b000ab05e585236455f1482a0bbf9</Sha>
+      <Sha>961b953eb77922d3906506ee15a58068abfa3284</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.NETCore.Platforms" Version="3.0.0-preview9.19416.11">
+    <Dependency Name="Microsoft.NETCore.Platforms" Version="3.0.0-preview9.19419.5">
       <Uri>https://github.com/dotnet/corefx</Uri>
-      <Sha>b3a4cdd6cd9b000ab05e585236455f1482a0bbf9</Sha>
+      <Sha>961b953eb77922d3906506ee15a58068abfa3284</Sha>
     </Dependency>
     <Dependency Name="Microsoft.NETCore.App" Version="3.0.0-preview9-19419-06">
       <Uri>https://github.com/dotnet/core-setup</Uri>

eng/Versions.props

@@ -21,8 +21,8 @@
     <!-- roslyn -->
     <MicrosoftNetCompilersToolsetVersion>3.3.0-beta2-19367-02</MicrosoftNetCompilersToolsetVersion>
     <!-- corefx -->
-    <MicrosoftPrivateCoreFxNETCoreAppVersion>4.6.0-preview9.19416.11</MicrosoftPrivateCoreFxNETCoreAppVersion>
-    <MicrosoftNETCorePlatformsVersion>3.0.0-preview9.19416.11</MicrosoftNETCorePlatformsVersion>
+    <MicrosoftPrivateCoreFxNETCoreAppVersion>4.6.0-preview9.19419.5</MicrosoftPrivateCoreFxNETCoreAppVersion>
+    <MicrosoftNETCorePlatformsVersion>3.0.0-preview9.19419.5</MicrosoftNETCorePlatformsVersion>
     <MicrosoftBclAsyncInterfacesVersion>1.0.0-preview7.19326.2</MicrosoftBclAsyncInterfacesVersion>
     <!-- core-setup -->
     <MicrosoftNETCoreAppVersion>3.0.0-preview9-19419-06</MicrosoftNETCoreAppVersion>