Fix ExplainTest in Windows (#468)

src/test/scala/com/microsoft/hyperspace/index/plananalysis/ExplainTest.scala

@@ -176,7 +176,7 @@ class ExplainTest extends SparkFunSuite with HyperspaceSuite {
       .replace("$end", displayMode.beginEndTag.close)
       .replace("$highlightBegin", displayMode.highlightTag.open)
       .replace("$highlightEnd", displayMode.highlightTag.close)
-      .replace("\n", displayMode.newLine)
+      .replace(System.lineSeparator(), displayMode.newLine)
 
     def filterQuery(query: DataFrame): DataFrame = {
       query.filter("Col2 == 2").select("Col1")