Revert replacement in trace

`trace` is made for multi-line output, since it has to show large parts of programs
accurately. Replacing newline with space does not work here. It messes up the layout
and changes the meaning of code.

Author: odersky

compiler/src/dotty/tools/dotc/reporting/trace.scala

@@ -76,7 +76,7 @@ trait TraceSyntax:
     else
       // Avoid evaluating question multiple time, since each evaluation
       // may cause some extra logging output.
-      val q = question.replace('\n', ' ')
+      val q = question
       val leading = s"==> $q?"
       val trailing = (res: T) => s"<== $q = ${showOp(res)}"
       var finalized = false