Fix code review feedback: use SymbolEqualityComparer for AsParallel methods

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.NetCore.Analyzers/Performance/DoNotUseAsParallelInForEachLoop.cs

@@ -52,8 +52,9 @@ private static void OnCompilationStart(CompilationStartAnalysisContext context)
                 return;
             }
 
-            // Get all AsParallel methods
-            var asParallelMethods = ImmutableHashSet.CreateRange(
+            // Get all AsParallel methods - use SymbolEqualityComparer for proper comparison
+            var asParallelMethods = ImmutableHashSet.CreateRange<IMethodSymbol>(
+                SymbolEqualityComparer.Default,
                 parallelEnumerableType.GetMembers("AsParallel").OfType<IMethodSymbol>());
 
             if (asParallelMethods.IsEmpty)