Autocompletion pop's up when deletion stops at the end of a valid symbol

[ankoh]

We could just just check if the current CodeMirror transaction was a deletion and stop autocompletion if the script cursor points to a new word.

https://github.com/ankoh/sqlynx/assets/3986510/8a165616-ac2e-4561-8144-b9cdda36b27d

Reported by @vogelsgesang