Fix test class name

Author: Gary Gregory

src/test/java/org/apache/commons/io/charset/CharsetDecodersTest.java

@@ -29,7 +29,7 @@
 /**
  * Tests {@link CharsetDecoders}.
  */
-public class CharsetDecdersTest {
+public class CharsetDecodersTest {
 
     @Test
     public void testToCharsetDecoders_default() {