Fixed a typo in the synopsis (noecept -> noexcept). Thanks to Kim for the catch

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@293079 91177308-0d34-0410-b5e6-96231b3b80d8

include/future

@@ -156,7 +156,7 @@ public:
     ~future();
     future& operator=(const future& rhs) = delete;
     future& operator=(future&&) noexcept;
-    shared_future<R> share() noecept;
+    shared_future<R> share() noexcept;
 
     // retrieving the value
     R get();