Update extend-ios.md (#223)

Update Extend iOS
diff --git a/source/cn/guide/extend-ios.md b/source/cn/guide/extend-ios.md
index 70bf438..9129647 100644
--- a/source/cn/guide/extend-ios.md
+++ b/source/cn/guide/extend-ios.md
@@ -296,7 +296,6 @@
 - (WXCoreAlignSelf)getCssStyleAlignSelf;
 - (WXCorePositionType)getCssStylePositionType;
 - (NSString*)convertLayoutValueToStyleValue:(NSString*)valueName;
-- (CGFloat)safeContainerStyleWidth;
  ```
 
 ## 自定义 handler