fix(doc): correct small errors in pipes.md

Fixes some minor language errors in documentation on pipes

Author: bepri

src/std_misc/process/pipe.md

@@ -1,6 +1,6 @@
 # Pipes
 
-The `std::Child` struct represents a running child process, and exposes the
+The `std::process::Child` struct represents a child process, and exposes the
 `stdin`, `stdout` and `stderr` handles for interaction with the underlying
 process via pipes.