Update ExtensionRepository.java

这里存在线程不安全的情况，改成ConcurrentHashMap

cola-components/cola-component-extension-starter/src/main/java/com/alibaba/cola/extension/ExtensionRepository.java

@@ -23,7 +23,7 @@ public Map<ExtensionCoordinate, ExtensionPointI> getExtensionRepo() {
         return extensionRepo;
     }
 
-    private Map<ExtensionCoordinate, ExtensionPointI> extensionRepo = new HashMap<>();
+    private Map<ExtensionCoordinate, ExtensionPointI> extensionRepo = new ConcurrentHashMap<>();
 
 
 }