Fix SqliteVectorStoreWriterTests hang: reduce test record count and use conditional MaxTopCount

test/Libraries/Microsoft.Extensions.DataIngestion.Tests/Writers/VectorStoreWriterTests.cs

@@ -134,10 +134,9 @@ public async Task IncrementalIngestion_WithManyRecords_DeletesAllPreExistingChun
 
         IngestionDocument document = new(documentId);
 
-        // Create more chunks than the MaxTopCount (1000) to test pagination
-        // We create 2500 chunks to ensure multiple batches
+        // Create enough chunks to exercise the incremental ingestion delete-all behavior
         List<IngestionChunk<string>> chunks = [];
-        for (int i = 0; i < 2500; i++)
+        for (int i = 0; i < 50; i++)
         {
             chunks.Add(new($"chunk {i}", document));
         }