onboarding: Improve Windows/Linux keyboard shortcuts; example ligature (#36712)

Small fixes to onboarding.
Correct ligature example.
Replace`ctrl-escape` and `alt-tab` since they are reserved on windows
(and often on linux) and so are caught by the OS.

Release Notes:

- N/A

crates/onboarding/src/editing_page.rs

@@ -606,7 +606,7 @@ fn render_popular_settings_section(
     cx: &mut App,
 ) -> impl IntoElement {
     const LIGATURE_TOOLTIP: &str =
-        "Font ligatures combine two characters into one. For example, turning =/= into ≠.";
+        "Font ligatures combine two characters into one. For example, turning != into ≠.";
 
     v_flex()
         .pt_6()