Rephrase an exception's message

Author: heyams

core/src/main/java/com/microsoft/applicationinsights/internal/perfcounter/ProcessPerformanceCountersModule.java

@@ -71,6 +71,6 @@ public void addConfigurationData(PerformanceCountersXmlElement configuration) {
             return;
         }
 
-        throw new IllegalStateException("Custom Performance Counter metrics is not enabled in Java 3.0 Agent.");
+        throw new IllegalStateException("Custom performance counter metrics have been disabled for Java 3.0+ Agent.");
     }
 }