[SPARK-26426][SQL] fix ExpresionInfo assert error in windows operation system.

## What changes were proposed in this pull request?
fix ExpresionInfo assert error in windows operation system, when running unit tests.

## How was this patch tested?
unit tests

Closes apache#23363 from yanlin-Lynn/unit-test-windows.

Authored-by: wangyanlin01 <[email protected]>
Signed-off-by: Hyukjin Kwon <[email protected]>

Author: wangyanlin01

sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionInfo.java

@@ -79,7 +79,7 @@ public ExpressionInfo(
         assert name != null;
         assert arguments != null;
         assert examples != null;
-        assert examples.isEmpty() || examples.startsWith("\n    Examples:");
+        assert examples.isEmpty() || examples.startsWith(System.lineSeparator() + "    Examples:");
         assert note != null;
         assert since != null;