Don't autofocus comment field with content editor

What does this MR do and why?

Autofocus of the textarea on load means shortcut keys don't work (up/down arrows of gitlab shortcuts). Maybe there are some places we want this (expanding discussions?), but not for initial page load.

How to set up and validate locally

1. Enable the flag

   Feature.enable(:content_editor_on_issues)

2. Visit any issue or MR
3. press down arrow

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

app/assets/javascripts/notes/components/comment_form.vue

@@ -364,7 +364,6 @@ export default {
                 :autosave-key="autosaveKey"
                 :disabled="isSubmitting"
                 supports-quick-actions
-                autofocus
                 @keydown.up="editCurrentUserLastNote()"
                 @keydown.meta.enter="handleEnter()"
                 @keydown.ctrl.enter="handleEnter()"