Fix a few linux keybindings that use cmd- instead of ctrl- (#32332)

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -35,7 +35,7 @@
       "ctrl-shift-f5": "debugger::Restart",
       "f6": "debugger::Pause",
       "f7": "debugger::StepOver",
-      "cmd-f11": "debugger::StepInto",
+      "ctrl-f11": "debugger::StepInto",
       "shift-f11": "debugger::StepOut",
       "f11": "zed::ToggleFullScreen",
       "ctrl-alt-z": "edit_prediction::RateCompletions",
@@ -267,8 +267,8 @@
   {
     "context": "AgentPanel && prompt_editor",
     "bindings": {
-      "cmd-n": "agent::NewTextThread",
-      "cmd-alt-t": "agent::NewThread"
+      "ctrl-n": "agent::NewTextThread",
+      "ctrl-alt-t": "agent::NewThread"
     }
   },
   {