Fix Issue886 test: remove blank lines between consecutive members

The VB source has no blank line between `End Structure` and `Class C`,
and no blank line between `Sub Foo` and `Sub Bar`. Line trivia mapping
preserves source blank-line layout, so the expected C# output must also
omit those blank lines (consistent with TestGenericInheritanceInGlobalNamespace
and TestMissingByRefArgumentWithNoExplicitDefaultValue).

https://claude.ai/code/session_01AkwUvu3XuCdj3D4axoX4UX

Author: claude

Tests/CSharp/ExpressionTests/ByRefTests.cs

@@ -981,13 +981,11 @@ End Class
 internal partial struct S
 {
 }
-
 internal partial class C
 {
     public void Foo([Optional] ref S s)
     {
     }
-
     public void Bar()
     {
         S args = default;