[libc++][NFC] Remove useless public: label at the end of class

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@357511 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/istream b/include/istream
index bedd738..e59ae2c 100644
--- a/include/istream
+++ b/include/istream
@@ -1297,7 +1297,6 @@
     inline _LIBCPP_HIDE_FROM_ABI_AFTER_V1
     void swap(basic_iostream& __rhs)
     { basic_istream<char_type, traits_type>::swap(__rhs); }
-public:
 };
 
 #ifndef _LIBCPP_CXX03_LANG