Move from Zed fonts to IBM Plex (#13596)

Release Notes:

- Changed the default fonts to IBM Plex Sans and IBM Plex Mono. If you'd
like to go back to using Zed Sans/Zed mono you need to
[download](https://github.com/zed-industries/zed-fonts/releases/tag/1.2.0)
them and install them.

crates/gpui/src/platform/cosmic_text/text_system.rs

@@ -205,7 +205,7 @@ impl CosmicTextSystemState {
     ) -> Result<SmallVec<[FontId; 4]>> {
         // TODO: Determine the proper system UI font.
         let name = if name == ".SystemUIFont" {
-            "Zed Sans"
+            "Zed Plex Sans"
         } else {
             name
         };

crates/gpui/src/text_system.rs

@@ -64,7 +64,7 @@ impl TextSystem {
             fallback_font_stack: smallvec![
                 // TODO: This is currently Zed-specific.
                 // We should allow GPUI users to provide their own fallback font stack.
-                font("Zed Mono"),
+                font("Zed Plex Mono"),
                 font("Helvetica"),
                 font("Cantarell"), // Gnome
                 font("Ubuntu"),    // Gnome (Ubuntu)

crates/gpui/src/text_system/line_wrapper.rs

@@ -154,12 +154,12 @@ mod tests {
         let cx = TestAppContext::new(dispatcher, None);
         cx.text_system()
             .add_fonts(vec![std::fs::read(
-                "../../assets/fonts/zed-mono/zed-mono-extended.ttf",
+                "../../assets/fonts/plex-mono/ZedPlexMono-Regular.ttf",
             )
             .unwrap()
             .into()])
             .unwrap();
-        let id = cx.text_system().font_id(&font("Zed Mono")).unwrap();
+        let id = cx.text_system().font_id(&font("Zed Plex Mono")).unwrap();
 
         cx.update(|cx| {
             let text_system = cx.text_system().clone();