[Blocks] Remove a block callback validation that's apparently too eager. (#20625)

The validation verifies that the function pointer for a block callback is the
same the return value from the method's
MethodInfo.MethodHandle.GetFunctionPointer() method.

In actual code, it's equivalent to validating that the following always prints "Equal: true":

```cs
[UnmanagedCallersOnly]
public static void Invoke () {}

static void Test ()
{
    delegate* unmanaged<void> fptr1 = &Invoke;
    IntPtr fptr2 = GetType ().GetMethod ("Invoke").MethodHandle.GetFunctionPointer ();
    Console.WriteLine ($"fptr1: 0x{((IntPtr) fptr1).ToString ("x")}");
    Console.WriteLine ($"fptr2: 0x{fptr2.ToString ("x")}");
    Console.WriteLine ($"Equal: ((IntPtr) fptr1) == fptr2}"); // prints "Equal: true" for me
}
```

However, this isn't documented, and some feedback indicates it's certainly not
a valid assumption for CoreCLR:

https://discord.com/channels/732297728826277939/732582981163548703/1242473425759633488

And there's also a customer running into this validation, apparently without cause:
https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2054534

So just remove it.

src/ObjCRuntime/Blocks.cs

@@ -172,11 +172,6 @@ namespace ObjCRuntime {
 			if (!Runtime.DynamicRegistrationSupported)
 				throw ErrorHelper.CreateError (8050, Errors.MX8050 /* BlockLiteral.GetBlockSignature is not supported when the dynamic registrar has been linked away. */);
 
-			// Verify that the function pointer matches the trampoline
-			var functionPointer = trampolineMethod.MethodHandle.GetFunctionPointer ();
-			if (functionPointer != (IntPtr) trampoline)
-				throw ErrorHelper.CreateError (8047, Errors.MX8047 /* The trampoline method {0} does not match the function pointer 0x{1} for the trampolineMethod argument (they're don't refer to the same method) */, trampolineMethod.DeclaringType.FullName + "." + trampolineMethod.Name, ((IntPtr) trampoline).ToString ("x"));
-
 			// Verify that there's at least one parameter, and it must be System.IntPtr, void* or ObjCRuntime.BlockLiteral*.
 			var parameters = trampolineMethod.GetParameters ();
 			if (parameters.Length < 1)

tools/mtouch/Errors.designer.cs

@@ -4168,15 +4168,6 @@ namespace Xamarin.Bundler {
             }
         }
         
-        /// <summary>
-        ///   Looks up a localized string similar to The trampoline method {0} does not match the function pointer 0x{1} for the trampolineMethod argument (they&apos;re don&apos;t refer to the same method)..
-        /// </summary>
-        public static string MX8047 {
-            get {
-                return ResourceManager.GetString("MX8047", resourceCulture);
-            }
-        }
-        
         /// <summary>
         ///   Looks up a localized string similar to The trampoline method {0} must have at least one parameter..
         /// </summary>

tools/mtouch/Errors.resx

@@ -2227,9 +2227,7 @@
 		<value>Unable to find the method '{0}' in the type '{1}'</value>
 	</data>
 
-	<data name="MX8047" xml:space="preserve">
-		<value>The trampoline method {0} does not match the function pointer 0x{1} for the trampolineMethod argument (they're don't refer to the same method).</value>
-	</data>
+	<!-- MX8047: unused -->
 
 	<data name="MX8048" xml:space="preserve">
 		<value>The trampoline method {0} must have at least one parameter.</value>