SLING-11108 - org.apache.sling.scripting.sightly.impl.engine.extension.FormatFilterExtensionTest#testDateFormatWithEscapedCharacters fails on newer JDKs

* make the test consistent by providing a set locale
diff --git a/src/test/java/org/apache/sling/scripting/sightly/impl/engine/extension/FormatFilterExtensionTest.java b/src/test/java/org/apache/sling/scripting/sightly/impl/engine/extension/FormatFilterExtensionTest.java
index f168883..9c33bc6 100644
--- a/src/test/java/org/apache/sling/scripting/sightly/impl/engine/extension/FormatFilterExtensionTest.java
+++ b/src/test/java/org/apache/sling/scripting/sightly/impl/engine/extension/FormatFilterExtensionTest.java
@@ -23,6 +23,7 @@
 import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 
 import javax.script.Bindings;
@@ -106,10 +107,10 @@
     @Test
     public void testDateFormatWithEscapedCharacters() {
         assumeJdk8LocaleData();
-        assertDate("01 December '18 12:00 AM; day in year: 335; week in year: 49",
+        assertDate("01 December '18 12:00 AM; day in year: 335; week in year: 48",
             "dd MMMM ''yy hh:mm a; 'day in year': D; 'week in year': w",
             "UTC",
-            null);
+            Locale.UK.toString());
     }
 
     /**
@@ -186,4 +187,4 @@
         }
         assertEquals(expected, subject.call(renderContext, format, options));
     }
-}
\ No newline at end of file
+}