Removed 1 unnecessary stubbings in ThreadPoolMetricsGaugesTest.java (#9)

diff --git a/src/test/java/org/apache/sling/commons/threads/impl/ThreadPoolMetricsGaugesTest.java b/src/test/java/org/apache/sling/commons/threads/impl/ThreadPoolMetricsGaugesTest.java
index 525cd07..bde7043 100644
--- a/src/test/java/org/apache/sling/commons/threads/impl/ThreadPoolMetricsGaugesTest.java
+++ b/src/test/java/org/apache/sling/commons/threads/impl/ThreadPoolMetricsGaugesTest.java
@@ -88,7 +88,6 @@
         when(bean.getMBeanInfo()).thenReturn(info);
         when(bean.getAttribute(eq(ATTR_A_NAME))).thenReturn(new Attributes().getA());
         when(bean.getAttribute(eq(ATTR_B_NAME))).thenReturn(new Attributes().getB());
-        when(bean.getAttribute(eq(ATTR_C_NAME))).thenReturn(new Attributes().getC());
         when(bean.getAttribute(eq(ATTR_D_NAME)))
                 .thenThrow(new JMRuntimeException("this exception is for unit test only"));