Change alt text reminder to not appear for private mentions in web UI (#33784)

app/javascript/mastodon/features/compose/components/compose_form.jsx

@@ -120,7 +120,7 @@ class ComposeForm extends ImmutablePureComponent {
       return;
     }
 
-    this.props.onSubmit(missingAltTextModal && this.props.missingAltText);
+    this.props.onSubmit(missingAltTextModal && this.props.missingAltText && this.props.privacy !== 'direct');
 
     if (e) {
       e.preventDefault();