[internal/release/3.1] Update dependencies from dnceng/internal/dotnet-winforms

eng/Version.Details.xml

 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.Private.Winforms" Version="4.8.1-servicing.21213.7">
-      <Uri>https://dev.azure.com/dnceng/internal/_git/dotnet-winforms</Uri>
-      <Sha>4159e19925152f3e6ef6b123d6c0b78f20044a72</Sha>
+    <Dependency Name="Microsoft.Private.Winforms" Version="4.8.1-servicing.21261.7">
+      <Uri>https://github.com/dotnet/winforms</Uri>
+      <Sha>d3e02ddb767e59202d32597401f985a4880a45ac</Sha>
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>

eng/Versions.props

@@ -18,7 +18,7 @@
   </PropertyGroup>
   <!-- NuGet Package Versions -->
   <PropertyGroup>
-    <MicrosoftPrivateWinformsVersion>4.8.1-servicing.21213.7</MicrosoftPrivateWinformsVersion>
+    <MicrosoftPrivateWinformsVersion>4.8.1-servicing.21261.7</MicrosoftPrivateWinformsVersion>
   </PropertyGroup>
   <!-- Packages that come from https://github.com/dotnet/coreclr -->
   <PropertyGroup>