Suppress IDE0031 (#13260)

* Suppress IDE0031 warnings in VMR

* Update src/System.Private.Windows.Core/src/System.Private.Windows.Core.csproj

Co-authored-by: Tanya Solyanik <[email protected]>

---------

Co-authored-by: Tanya Solyanik <[email protected]>

Author: NikolaMilosavljevic

src/System.Private.Windows.Core/src/System.Private.Windows.Core.csproj

@@ -21,6 +21,9 @@
       SYSLIB5005: System.Formats.Nrbf is experimental
     -->
     <NoWarn>$(NoWarn);CS3016;SYSLIB5005</NoWarn>
+    <!-- Reenable when SDK and dotnet Preview 4 versions flow into this repo and we are in sync with VMR. -->
+    <!-- tracking https://github.com/dotnet/winforms/issues/13261 -->
+    <NoWarn Condition="'$(DotNetBuild)' == 'true'">$(NoWarn);IDE0031</NoWarn>
     <Deterministic>true</Deterministic>
     <ProduceReferenceAssembly>true</ProduceReferenceAssembly>
     <UsePublicApiAnalyzers>false</UsePublicApiAnalyzers>

src/System.Windows.Forms/System.Windows.Forms.csproj

@@ -15,6 +15,8 @@
       SYSLIB5005: System.Formats.Nrbf is experimental
     -->
     <NoWarn>$(NoWarn);SYSLIB5005</NoWarn>
+    <!-- Reenable when fixes are made for IDE0031 warnings that VMR treats as errors. -->
+    <NoWarn Condition="'$(DotNetBuild)' == 'true'">$(NoWarn);IDE0031</NoWarn>
     <Win32Manifest>Resources\System\Windows\Forms\XPThemes.manifest</Win32Manifest>
     <Deterministic>true</Deterministic>
     <ProduceReferenceAssembly>true</ProduceReferenceAssembly>