Update test expectation of NegatedClassMemberTest for Windows bot

Change-Id: If522408f15b27ade27ad247701433471c6bb68c3
diff --git a/src/test/java/com/android/tools/r8/proguard/rules/NegatedClassMemberTest.java b/src/test/java/com/android/tools/r8/proguard/rules/NegatedClassMemberTest.java
index 27747f5..520e1d8 100644
--- a/src/test/java/com/android/tools/r8/proguard/rules/NegatedClassMemberTest.java
+++ b/src/test/java/com/android/tools/r8/proguard/rules/NegatedClassMemberTest.java
@@ -78,7 +78,8 @@
                       + ", Unexpected character '!': "
                       + "The negation character can only be used to negate access flags"),
               containsString(
-                  StringUtils.joinLines(
+                  StringUtils.join(
+                      "\n",
                       "-keepclasseswithmembers class ** { long x; !long y; }",
                       "                                           ^"))));
     }