Remove the unused method. & Modify doc. (#2692)

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/conf/SnifferConfigInitializer.java

@@ -52,7 +52,7 @@ public class SnifferConfigInitializer {
     /**
      * If the specified agent config path is set, the agent will try to locate the specified agent config. If the
      * specified agent config path is not set , the agent will try to locate `agent.config`, which should be in the
-     * /config dictionary of agent package.
+     * /config directory of agent package.
      * <p>
      * Also try to override the config by system.properties. All the keys in this place should
      * start with {@link #ENV_KEY_PREFIX}. e.g. in env `skywalking.agent.service_name=yourAppName` to override

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginResourcesResolver.java

@@ -55,26 +55,4 @@ public class PluginResourcesResolver {
         }
         return null;
     }
-
-    /**
-     * Get the classloader.
-     * First getDefault current thread's classloader,
-     * if fail, getDefault {@link PluginResourcesResolver}'s classloader.
-     *
-     * @return the classloader to find plugin definitions.
-     */
-    private ClassLoader getDefaultClassLoader() {
-        ClassLoader cl = null;
-        try {
-            cl = Thread.currentThread().getContextClassLoader();
-        } catch (Throwable ex) {
-            // Cannot access thread context ClassLoader - falling back to system class loader...
-        }
-        if (cl == null) {
-            // No thread context class loader -> use class loader of this class.
-            cl = PluginResourcesResolver.class.getClassLoader();
-        }
-        return cl;
-    }
-
 }