Replace outdated Array.Empty comments with correct reason (#123862)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
Co-authored-by: Stephen Toub <stoub@microsoft.com>

Author: Copilot

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableArray_1.Minimal.cs

@@ -39,8 +39,7 @@ public partial struct ImmutableArray<T> : IEnumerable<T>, IEquatable<ImmutableAr
         /// An empty (initialized) instance of <see cref="ImmutableArray{T}"/>.
         /// </summary>
 #pragma warning disable CA1825
-        // Array.Empty<T>() doesn't exist in all configurations
-        // Switching to Array.Empty also has a non-negligible impact on the working set memory
+        // Avoid the extra generic instantiation for Array.Empty<T>()
         public static readonly ImmutableArray<T> Empty = new ImmutableArray<T>(new T[0]);
 #pragma warning restore CA1825
 

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -58,7 +58,7 @@ internal ActivityChangedEventArgs(Activity? previous, Activity? current)
     [DebuggerTypeProxy(typeof(ActivityDebuggerProxy))]
     public partial class Activity : IDisposable
     {
-#pragma warning disable CA1825 // Array.Empty<T>() doesn't exist in all configurations
+#pragma warning disable CA1825 // avoid the extra generic instantiation for Array.Empty<T>()
         private static readonly IEnumerable<KeyValuePair<string, string?>> s_emptyBaggageTags = new KeyValuePair<string, string?>[0];
         private static readonly IEnumerable<KeyValuePair<string, object?>> s_emptyTagObjects = new KeyValuePair<string, object?>[0];
         private static readonly IEnumerable<ActivityLink> s_emptyLinks = new DiagLinkedList<ActivityLink>();

src/libraries/System.Threading.Tasks.Dataflow/src/Internal/ImmutableArray.cs

@@ -25,7 +25,7 @@ namespace System.Threading.Tasks.Dataflow.Internal
     internal readonly struct ImmutableArray<T>
     {
         /// <summary>An empty array.</summary>
-#pragma warning disable CA1825 // Array.Empty<T>() doesn't exist in all configurations
+#pragma warning disable CA1825 // avoid the extra generic instantiation for Array.Empty<T>()
         private static readonly ImmutableArray<T> s_empty = new ImmutableArray<T>(new T[0]);
 #pragma warning restore CA1825
         /// <summary>The immutable data in this array instance.</summary>