Update target framework from net7 to net8.

Author: Konard

csharp/Platform.Diagnostics/Platform.Diagnostics.csproj

@@ -23,9 +23,7 @@
     <IncludeSymbols>true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
     <LangVersion>latest</LangVersion>
-    <PackageReleaseNotes>Lowest supported version of .NET Framework is now 4.7.2.
-Issues fix.
-Tests added.</PackageReleaseNotes>
+    <PackageReleaseNotes>Update target framework from net7 to net8.</PackageReleaseNotes>
     <Nullable>enable</Nullable>
   </PropertyGroup>