keymap: Fix subword navigation and selection on Sublime Text keymap (#31840)
On Linux, the correct modifier key for this action is `alt`, not `ctrl`.
I mistakenly set it to `ctrl` on #30268.
From Sublime's keymap:
```json
{ "keys": ["ctrl+left"], "command": "move", "args": {"by": "words", "forward": false} },
{ "keys": ["ctrl+right"], "command": "move", "args": {"by": "word_ends", "forward": true} },
{ "keys": ["ctrl+shift+left"], "command": "move", "args": {"by": "words", "forward": false, "extend": true} },
{ "keys": ["ctrl+shift+right"], "command": "move", "args": {"by": "word_ends", "forward": true, "extend": true} },
{ "keys": ["alt+left"], "command": "move", "args": {"by": "subwords", "forward": false} },
{ "keys": ["alt+right"], "command": "move", "args": {"by": "subword_ends", "forward": true} },
{ "keys": ["alt+shift+left"], "command": "move", "args": {"by": "subwords", "forward": false, "extend": true} },
{ "keys": ["alt+shift+right"], "command": "move", "args": {"by": "subword_ends", "forward": true, "extend": true} },
```
Release Notes:
- N/A
58a400b1ee