Drive-by Docs Fixes: bevy_picking, bevy_text (#16946)

Noticed these were either incomplete or inconsistent, so I
fixed/augmented them.

crates/bevy_picking/src/lib.rs

@@ -121,11 +121,11 @@
 //!
 //! You will eventually need to choose which picking backend(s) you want to use. This crate does not
 //! supply any backends, and expects you to select some from the other bevy crates or the third-party
-//! ecosystem. You can find all the provided backends in the [`backend`] module.
+//! ecosystem.
 //!
 //! It's important to understand that you can mix and match backends! For example, you might have a
 //! backend for your UI, and one for the 3d scene, with each being specialized for their purpose.
-//! This crate provides some backends out of the box, but you can even write your own. It's been
+//! Bevy provides some backends out of the box, but you can even write your own. It's been
 //! made as easy as possible intentionally; the `bevy_mod_raycast` backend is 50 lines of code.
 //!
 //! #### Focus ([`focus`])

crates/bevy_text/src/text.rs

@@ -232,7 +232,8 @@ impl From<String> for TextSpan {
 /// This only affects the internal positioning of the lines of text within a text entity and
 /// does not affect the text entity's position.
 ///
-/// _Has no affect on a single line text entity._
+/// _Has no affect on a single line text entity_, unless used together with a
+/// [`TextBounds`](super::bounds::TextBounds) component with an explicit `width` value.
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash, Reflect, Serialize, Deserialize)]
 #[reflect(Serialize, Deserialize)]
 pub enum JustifyText {