Remove call to First with call to indexer

src/NetAnalyzers/Core/Microsoft.NetCore.Analyzers/Performance/DoNotGuardDictionaryRemoveByContainsKey.Fixer.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
 
 using System.Collections.Immutable;
-using System.Linq;
 using System.Threading.Tasks;
 using Analyzer.Utilities;
 using Microsoft.CodeAnalysis;
@@ -30,7 +29,7 @@ public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
                 return;
             }
 
-            var diagnostic = context.Diagnostics.First();
+            var diagnostic = context.Diagnostics[0];
             var conditionalOperationSpan = diagnostic.AdditionalLocations[0];
             var childLocation = diagnostic.AdditionalLocations[1];
             if (root.FindNode(conditionalOperationSpan.SourceSpan) is not SyntaxNode conditionalSyntax ||