fixes #11048

## Problem
in the situation `press right`, `press left`, `release right` the
following happens right now:

- `keypressed right`, `current_keysym` is set to `right`
- `keypressed left`, `current_keysym` is set to `left`

the repeat timer runs asynchronously and emits keyrepeats since
`current_keysym.is_some()`

- `keyreleased right`, `current_keysym` is set to None

the repeat timer no longer emits keyrepeats

- `keyreleased left`, this is where `current_keysym` should actually be
set to None.

## Solution
Only reset `current_keysym` if the released key matches the last pressed
key.

Release Notes:

- N/A