finance/electrum: Update 4.6.2 => 4.8.1

Release Notes:
https://github.com/spesmilo/electrum/blob/4.8.1/RELEASE-NOTES

PR: 297503
Security: CVE-2012-2459
Security: GHSA-vw94-r84p-66qf
Security: GHSA-q7m2-785w-r585
Sponsored by: UNIS Labs
MFH: 2026Q3