Make CosmicTextSystem Linux-only (#14728)

Since `WindowsDispatcher` requires a minimum Windows version of Windows
10 Fall Creators Update (10.0.16299), and the `alacritty_terminal`
dependency relies on conPTY, an API introduced in the same version,
additionally, `DirectWriteTextSystem` also relies on Windows 10 Fall
Creators Update (10.0.16299), so it seems reasonable to make
`CosmicTextSystem` Linux-only. And we can use `DirectWriteTextSystem` on
the Windows platform exclusively. I hope this approach makes sense.

Release Notes:

- N/A

crates/gpui/src/platform/windows/platform.rs

@@ -49,7 +49,7 @@ pub(crate) struct WindowsPlatform {
     icon: HICON,
     background_executor: BackgroundExecutor,
     foreground_executor: ForegroundExecutor,
-    text_system: Arc<dyn PlatformTextSystem>,
+    text_system: Arc<DirectWriteTextSystem>,
     clipboard_hash_format: u32,
     clipboard_metadata_format: u32,
 }
@@ -90,13 +90,8 @@ impl WindowsPlatform {
         let dispatcher = Arc::new(WindowsDispatcher::new());
         let background_executor = BackgroundExecutor::new(dispatcher.clone());
         let foreground_executor = ForegroundExecutor::new(dispatcher);
-        let text_system = if let Some(direct_write) = DirectWriteTextSystem::new().log_err() {
-            log::info!("Using direct write text system.");
-            Arc::new(direct_write) as Arc<dyn PlatformTextSystem>
-        } else {
-            log::info!("Using cosmic text system.");
-            Arc::new(CosmicTextSystem::new()) as Arc<dyn PlatformTextSystem>
-        };
+        let text_system =
+            Arc::new(DirectWriteTextSystem::new().expect("Error creating DirectWriteTextSystem"));
         let icon = load_icon().unwrap_or_default();
         let state = RefCell::new(WindowsPlatformState::new());
         let raw_window_handles = RwLock::new(SmallVec::new());