[BUGFIX] Text/plain outputs always in unicode

src/test/java/net/sourceforge/plantuml/servlet/TestMap.java

@@ -19,7 +19,7 @@ public class TestMap extends WebappTestCase {
         // Analyze response
         // Verifies the Content-Type header
         assertEquals("Response content type is not TEXT PLAIN", "text/plain", response.getContentType()); 
-        assertEquals("Response character set is not ISO-8859-1", "ISO-8859-1", response.getCharacterSet());
+        assertEquals("Response character set is not UTF-8", "UTF-8", response.getCharacterSet());
         // Get the content, check its first characters and verify its size
         String diagram = response.getText();
         assertTrue("Response content is not starting with <area", diagram.startsWith("<area"));