(core) Remove empty keyboard shortcut for command that shouldn't have one

Test Plan: Tested manually that strange-looking shortcut line for "Detach active editor" is gone.

Reviewers: jarek

Reviewed By: jarek

Differential Revision: https://phab.getgrist.com/D4148

app/client/components/commandList.ts

@@ -431,7 +431,7 @@ export const groups: CommendGroupDef[] = [{
       desc: 'Finish editing a cell, saving the value'
     }, {
       name: 'detachEditor',
-      keys: [''],
+      keys: [],
       desc: 'Detach active editor'
     }, {
       name: 'fieldEditSaveHere',