gpui: Send correct kill signal on Linux (#16797)

should be kill -0 (zero) instead

Related to #14291 and #14310

Release Notes:

- N/A

crates/gpui/src/platform/linux/platform.rs

@@ -184,7 +184,7 @@ impl<P: LinuxClient + 'static> Platform for P {
         // cleaned up when `kill -0` returns.
         let script = format!(
             r#"
-            while kill -O {pid} 2>/dev/null; do
+            while kill -0 {pid} 2>/dev/null; do
                 sleep 0.1
             done