project_panel: Remove cmd-opt-. binding for hiding hidden files (#43091)

Lots of folks were accidentally clicking this. Even though it’s the
default in macOS Finder, it’s a good idea to not have it as the default
for us.

Release Notes:

- Removed the default `cmd-opt-.` binding for toggling hidden files in
the Project Panel so it’s harder to hide them by accident.

assets/keymaps/default-linux.json

@@ -43,8 +43,7 @@
       "f11": "zed::ToggleFullScreen",
       "ctrl-alt-z": "edit_prediction::RateCompletions",
       "ctrl-alt-shift-i": "edit_prediction::ToggleMenu",
-      "ctrl-alt-l": "lsp_tool::ToggleMenu",
-      "ctrl-alt-.": "project_panel::ToggleHideHidden"
+      "ctrl-alt-l": "lsp_tool::ToggleMenu"
     }
   },
   {