Long-press delay for typing special chars with the on-screen keyboard is too long

Initially reported on #10263-note_10.

The GNOME on-screen keyboard allows e.g. long-pressing uao -> menu where the umlaut version can be inserted.

One of us tried this long-press thing after being suggested this by an Android user, and initially thought it did not work because he expected a shorter delay.

Let’s see if we can easily fix that or if we need to document it somehow.

Related issues

• Blocks #16080 (closed)

Original created by @intrigeri on 14753 (Redmine)