std::thread docs: fix link to current()

Author: SimonSapin

src/libstd/thread/mod.rs

@@ -158,7 +158,7 @@
 //! [`Err`]: ../../std/result/enum.Result.html#variant.Err
 //! [`panic!`]: ../../std/macro.panic.html
 //! [`Builder`]: ../../std/thread/struct.Builder.html
-//! [`thread::current`]: ../../std/thread/fn.spawn.html
+//! [`thread::current`]: ../../std/thread/fn.current.html
 //! [`Thread`]: ../../std/thread/struct.Thread.html
 //! [`park`]: ../../std/thread/fn.park.html
 //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark