Log Message:
Update finance/electrum to 4.0.9

# Release 4.0.9 - (Dec 18, 2020)
 * fixes a regression introduced in 4.0.8, that prevents from
   paying BIP70 invoices (#6859)
 * reflect frozen channels and disconnected peers in the displayed
   'can send/can receive' amounts.

# Release 4.0.8 - (Dec 17, 2020)
 * fix decoding BIP21 URIs with uppercase schema (d40bedb2)
 * psbt: put full derivation paths into PSBT by default (c8155129)
 * invoices: allow address-reuse (#6609, #6852)
 * A few other minor bugfixes.

# Release 4.0.7 - (Dec 9, 2020)
 * kivy: fix open channel with 'max' amount
 * kivy: fix regression introduced in last release (a9fc440)
 * other minor GUI fixes
 * Dependencies: as part of adapting to new dnspython (#6828),
   - python-ecdsa is no longer needed at all,
   - cryptography is now required (min 2.6), the user can no
     longer choose between cryptography and pycryptodomex

# Release 4.0.6 - (Dec 4, 2020)
 * Fix 'Max' button issue for submarine swaps button (#6770)
 * Fix 'Max' button in kivy (#6169)
 * Various fixes for Kivy/Android install wizard
 * More robust account keypath for BitBox02 (#6766)

# Release 4.0.5 - (Nov 18, 2020)
 * Fix .dmg binary hanging on recently released macOS 11 Big Sur (#6461)
 * Lightning:
   - bugfix: during LN channel opening, if the client crashed at the
     wrong moment, the channel might not get fully persisted to disk,
     and would need manual console-tinkering to recover (#6656)
   - Lightning is enabled by default. Electrum will not connect to
     the Lightning Network until the user opens a channel. (#6639)
   - smarter node recommendation (to open channels with) (#6705)
 * user interface: some minor changes that aim to improve usability
 * Ledger:
   - fix enumerating devices with new bitcoin app (1.5.1) (b78cbcff)
   - fix compat with HW.1 (200f547a)
 * A few other minor bugfixes.