Some markdown-formatted remarks are ported into triple slash comments with invalid structure

As seen in `MemoryManager` from `System.Memory` in `dotnet/runtime`, some `` sections are getting produced with invalid structure, and duplicated content.

From `` `MemoryManager`1.xml` ``

```xml

The type of items in the memory buffer managed by this memory manager.
An abstract base class that is used to replace the implementation of .

` class is used to extend the knowledge of types that is able to represent. For example, you can derive from `MemoryManager` to allow to be backed by a .

> [!NOTE]
> The `MemoryManager` class is intended for advanced scenarios. Most developers do not need to use it.

]]>


```

Before porting the docs into triple slash comments, this was the content of `MemoryManager.cs`:

```csharp
///
/// Manager of that provides the implementation.
///
public abstract class MemoryManager : IMemoryOwner, IPinnable
```

After porting, this is the result:

```csharp
/// An abstract base class that is used to replace the implementation of .
/// The type of items in the memory buffer managed by this memory manager.
/// The `MemoryManager` class is used to extend the knowledge of types that is able to represent. For example, you can derive from `MemoryManager` to allow to be backed by a .
/// [!NOTE]
/// > The `MemoryManager` class is intended for advanced scenarios. Most developers do not need to use it.
/// ]]>
public abstract class MemoryManager : IMemoryOwner, IPinnable
```

The `` section has the content duplicated, once inside the `` and once before it, which is an invalid structure.