chore: Fix nightly build errors that occurred on .NET 9 SDK Preview 5

[filzrev]

This PR intended to fix nightly build error that occurred after CI build is updated to .NET 9 SDK Preview 5.

Warning Message

CS9220 One or more overloads of method 'Create' having non-array params collection parameter might be applicable only in expanded form which is not supported during dynamic dispatch. Docfx.Build.SchemaDriven (net9.0)

Above warning occurred when passing dynamic variable to ImmutableArray.Create. So I've added type cast logics.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 78.85%. Comparing base (fe673ec) to head (3b2bb9a). Report is 201 commits behind head on main.

Files	Patch %	Lines
...uild.SchemaDriven/SchemaDrivenDocumentProcessor.cs	0.00%	2 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #10007 +/- ## ========================================== + Coverage 74.31% 78.85% +4.53% ========================================== Files 536 540 +4 Lines 23189 23477 +288 Branches 4056 4066 +10 ========================================== + Hits 17234 18512 +1278 + Misses 4853 3823 -1030 - Partials 1102 1142 +40 ```

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