Fix alt-t context (#18783)

- Fix incorrect context introduced in https://github.com/zed-industries/zed/pull/18749/

Release Notes:

- N/A

assets/keymaps/default-macos.json

@@ -444,7 +444,7 @@
     }
   },
   {
-    "context": "Editor && !Terminal",
+    "context": "Workspace && !Terminal",
     "bindings": {
       "alt-t": "task::Rerun",
       "alt-shift-t": "task::Spawn"