Calling a member inferred from a reference-typed generic constraint unnecessarily boxes the value.

When calling a method on a generic value that is constrained to be a reference type, the compiler mistakenly emits a `box` and `unbox.any` sequence of commands.

**Repro steps**

Compile the following function:

``` fsharp
let getDelegateMethod<'TDelegate when 'TDelegate :> System.Delegate> (del: 'TDelegate) = del.Method
```

**Expected behavior**

The generated IL should be:

```
ldarg.0
callvirt instance class [System.Private.CoreLib]System.Reflection.MethodInfo [System.Private.CoreLib]System.Delegate::get_Method()
ret
```

**Actual behavior**

The generated IL is:

```
ldarg.0
box !!TDelegate
unbox.any [System.Private.CoreLib]System.Delegate
callvirt instance class [System.Private.CoreLib]System.Reflection.MethodInfo [System.Private.CoreLib]System.Delegate::get_Method()
ret
```

**Known workarounds**

None

**Related information**

Calling the method using `constrained.callvirt` is not necessary; we surely have a reference type and just a `callvirt` suffices.

* .NET Runtime kind: .NET SDK 5.0.100