C#: Add some dummy db stats for the new expression kinds.

csharp/ql/lib/semmlecode.csharp.dbscheme.stats

@@ -948,6 +948,14 @@
             <k>@utf8_string_literal_expr</k>
             <v>4152</v>
         </e>
+        <e>
+            <k>@collection_expr</k>
+            <v>0</v>
+        </e>
+        <e>
+            <k>@spread_element_expr</k>
+            <v>0</v>
+        </e>
         <e>
             <k>@define_symbol_expr</k>
             <v>40236</v>