C#: Address review comments.

Author: calumgrant

csharp/extractor/Semmle.Extraction/Context.cs

@@ -165,7 +165,7 @@ public Entity CreateNonNullEntity<Type, Entity>(ICachedEntityFactory<Type, Entit
             if (init is null) throw new ArgumentException("Unexpected null value", nameof(init));
 
             if (objectEntityCache.TryGetValue(init, out var cached))
-                return (Entity)cached!;
+                return (Entity)cached;
 
             using (StackGuard)
             {

csharp/extractor/Semmle.Extraction/Id.cs

@@ -34,12 +34,7 @@ public class FreshId : IId
 
         public override string ToString() => "*";
 
-        public override bool Equals(object? obj)
-        {
-            // Expand logic to allow for nullability control flow analysis
-            if (obj is null) return false;
-            return obj.GetType() == GetType();
-        }
+        public override bool Equals(object? obj) => obj?.GetType() == GetType();
 
         public override int GetHashCode() => 0;