Migrate F# TFM to 9.0 following update changes

Files should point to 9, not 8.0 directories now. See #42308

Co-Authored-By: Chet Husk <[email protected]>

Author: nagilson

src/Layout/tool_fsharp/tool_fsc.csproj

@@ -17,7 +17,7 @@
     <PropertyGroup>
         <FSharpCorePath Condition="'$(DotNetFinalVersionKind)'!='release'">Shipping</FSharpCorePath>
         <FSharpCorePath Condition="'$(DotNetFinalVersionKind)'=='release'">Release</FSharpCorePath>
-        <FSharpTfm>net8.0</FSharpTfm>
+        <FSharpTfm>net9.0</FSharpTfm>
         <!-- In full product source-only mode, fsharp currently builds net9.0. In repo source-only modes, non VMR builds, or MSFT VMR builds,
              it's net8.0. -->
         <FSharpTfm Condition="'$(DotNetBuildSourceOnly)' == 'true' and '$(DotNetBuildOrchestrator)' == 'true'">net9.0</FSharpTfm>