fix: Remove duplicate LazyLock example.

The top-level docs for `LazyLock` included two lines of code, each
with an accompanying comment, that were identical and with nearly-
identical comments. This looks like an oversight from a past edit
which was perhaps trying to rewrite an existing example but ended
up duplicating rather than replacing, though I haven't gone back
through the Git history to check.

This commit removes what I personally think is the less-clear of
the two examples.

Signed-off-by: Andrew Lilley Brinker <alilleybrinker@gmail.com>

library/std/src/sync/lazy_lock.rs

@@ -44,8 +44,6 @@ union Data<T, F> {
 ///
 /// // The `String` is built, stored in the `LazyLock`, and returned as `&String`.
 /// let _ = &*DEEP_THOUGHT;
-/// // The `String` is retrieved from the `LazyLock` and returned as `&String`.
-/// let _ = &*DEEP_THOUGHT;
 /// ```
 ///
 /// Initialize fields with `LazyLock`.