chore: Fix some violations of 'needless_pass_by_ref_mut' lint (#18795)

While this lint is allow-by-default, it seems pretty useful to get rid
of mutable borrows when they're not needed.

Closes #ISSUE

Release Notes:

- N/A

crates/zed/src/zed.rs

@@ -573,7 +573,7 @@ fn feature_gate_zed_pro_actions(cx: &mut AppContext) {
     .detach();
 }
 
-fn initialize_pane(workspace: &mut Workspace, pane: &View<Pane>, cx: &mut ViewContext<Workspace>) {
+fn initialize_pane(workspace: &Workspace, pane: &View<Pane>, cx: &mut ViewContext<Workspace>) {
     pane.update(cx, |pane, cx| {
         pane.toolbar().update(cx, |toolbar, cx| {
             let multibuffer_hint = cx.new_view(|_| MultibufferHint::new());
@@ -981,7 +981,7 @@ fn open_telemetry_log_file(workspace: &mut Workspace, cx: &mut ViewContext<Works
 }
 
 fn open_bundled_file(
-    workspace: &mut Workspace,
+    workspace: &Workspace,
     text: Cow<'static, str>,
     title: &'static str,
     language: &'static str,