Fix typo in style.rs (#5845)

lien -> line

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crates/egui/src/style.rs

@@ -989,7 +989,7 @@ pub struct Visuals {
     /// Show a background behind collapsing headers.
     pub collapsing_header_frame: bool,
 
-    /// Draw a vertical lien left of indented region, in e.g. [`crate::CollapsingHeader`].
+    /// Draw a vertical line left of indented region, in e.g. [`crate::CollapsingHeader`].
     pub indent_has_left_vline: bool,
 
     /// Whether or not Grids and Tables should be striped by default