Use US English spelling of "behavior" and "customize" (#15117)

This PR fixes some instances that weren't using US English spellings of
"behavior" and "customize".

Release Notes:

- N/A

crates/outline_panel/src/outline_panel_settings.rs

@@ -30,7 +30,7 @@ pub struct OutlinePanelSettingsContent {
     ///
     /// Default: true
     pub button: Option<bool>,
-    /// Customise default width (in pixels) taken by outline panel
+    /// Customize default width (in pixels) taken by outline panel
     ///
     /// Default: 240
     pub default_width: Option<f32>,