[Bug] Metadata extracted from DLL does not include triple slash comments

**Describe the bug**
When I create a doc site using DocFx I get different results if I reference a DLL versus a CSPROJ. Using the DLL as a metadata source looses the '///' comments

**To Reproduce**
Steps to reproduce the behavior:
1. Clone the repository at [BlazorBounce](https://github.com/Material-Blazor/BlazorBounce)
2. From the root run ServeDocs
3. Observe the output, there are no /// comments
4. Change the source spec to be the csproj
5. Run ServeDocs again
6. Observe /// comments

**Expected behavior**
I expect the output to be the same or that documentation be added that states that /// comments aren't available when metadata is extracted from a DLL

**Context (please complete the following information):**
- OS: Windows 11
- Docfx version: 2.77.0

**Additional context**
Add any other context about the problem here.