Make doc for stdin field of process consistent

The other fields use this format and example.

library/std/src/process.rs

@@ -169,15 +169,15 @@ use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
 pub struct Child {
     pub(crate) handle: imp::Process,
 
-    /// The handle for writing to the child's standard input (stdin), if it has
-    /// been captured. To avoid partially moving
-    /// the `child` and thus blocking yourself from calling
-    /// functions on `child` while using `stdin`,
-    /// you might find it helpful:
+    /// The handle for writing to the child's standard input (stdin), if it
+    /// has been captured. You might find it helpful to do
     ///
     /// ```compile_fail,E0425
     /// let stdin = child.stdin.take().unwrap();
     /// ```
+    ///
+    /// to avoid partially moving the `child` and thus blocking yourself from calling
+    /// functions on `child` while using `stdin`.
     #[stable(feature = "process", since = "1.0.0")]
     pub stdin: Option<ChildStdin>,