[Bug] Markdown Metadata Output For Generic Classes Doesn't Show Derived Section

[MarcosCosmos]

Describe the bug
Not sure why, but the markdown metadata output format doesn't seem to include a Derived section on pages that happen to be generic, even though they would be listed in the yaml counterpart.

To Reproduce
Steps to reproduce the behavior:

1. Create a dummy project with a generic base class and one or more derived classes, e.g.:

namespace DocFXTest;
public class GenericBaseClass<T>
{
}

public class GenericDerivedClass<T> : GenericBaseClass<T>
{
}

2. Run DocFX with a minimal config for the project, i.e.:

{
  "metadata": [
    {
      "src": [
           ...
      ],
      "dest": ...
     }
  ]
}

4. Observe that the derivedClasses section is present in DocFXTest.GenericBaseClass-1.yml:

...
  derivedClasses:
  - DocFxTest.GenericDerivedClass`1
...

5. Modify the config to make the outputFormat markdown:

{
  "metadata": [
    {
      ...
      "outputFormat": "markdown"
     }
  ]
}

6. Run DocFX again.
   Expected behavior
   One of the resulting files, DocFXTest.GenericBaseClass-1.md, should have a Derived section, i.e.:

...
#### Derived
[GenericDerivedClass<T\>](DocFxTest.GenericDerivedClass\-1.md)
...

Actual behavior
DocFXTest.GenericBaseClass-1.md, does not have a Derived section, i.e.:

# <a id="DocFxTest_GenericBaseClass_1"></a> Class GenericBaseClass<T\>

Namespace: [DocFxTest](DocFxTest.md)  
Assembly: DocFxTest.dll

```csharp
public class GenericBaseClass<T>
```

#### Type Parameters

`T` 

#### Inheritance

[object](https://learn.microsoft.com/dotnet/api/system.object) ← 
[GenericBaseClass<T\>](DocFxTest.GenericBaseClass\-1.md)

#### Inherited Members

[object.Equals\(object?\)](https://learn.microsoft.com/dotnet/api/system.object.equals\#system\-object\-equals\(system\-object\)), 
[object.Equals\(object?, object?\)](https://learn.microsoft.com/dotnet/api/system.object.equals\#system\-object\-equals\(system\-object\-system\-object\)), 
[object.GetHashCode\(\)](https://learn.microsoft.com/dotnet/api/system.object.gethashcode), 
[object.GetType\(\)](https://learn.microsoft.com/dotnet/api/system.object.gettype), 
[object.MemberwiseClone\(\)](https://learn.microsoft.com/dotnet/api/system.object.memberwiseclone), 
[object.ReferenceEquals\(object?, object?\)](https://learn.microsoft.com/dotnet/api/system.object.referenceequals), 
[object.ToString\(\)](https://learn.microsoft.com/dotnet/api/system.object.tostring)

Context (please complete the following information):

• Docfx version: 2.77.0
• Template: markdown (api output format)

Additional context
The trigger condition appears to be the base class that is generic, and only that page is affected. Non-generic base classes will include a #### Derived section.

[filzrev]

I've also confirmed it can be reproduced when using "outputFormat": "apiPage".

It seems there is a problem on following logics.
https://github.com/dotnet/docfx/blob/main/src/Docfx.Dotnet/DotnetApiCatalog.ApiPage.cs#L398

When BaseType is generic class.
It seems SymbolEqualityComparer.Default.Equals always returns false.

It need to compare BaseType.OriginalDefinition instance instead.