fix: incorrect idx on Journals after reconciliation

[ruthra-kumar]

When reconciling Journal Entries, the newly created rows in Journal have incorrect idx value. Fixing here.

[codecov]

Codecov Report

Merging #36126 (72f577a) into develop (c16a581) will increase coverage by 0.00%.
The diff coverage is 60.71%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #36126   +/-   ##
========================================
  Coverage    64.20%   64.21%           
========================================
  Files          785      785           
  Lines        60703    60681   -22     
========================================
- Hits         38975    38965   -10     
+ Misses       21728    21716   -12     

Impacted Files	Coverage Δ
...ange_rate_revaluation/exchange_rate_revaluation.py	55.98% <0.00%> (ø)
erpnext/stock/doctype/item/item.py	85.66% <0.00%> (ø)
erpnext/assets/doctype/asset/depreciation.py	81.31% <23.07%> (ø)
erpnext/controllers/stock_controller.py	82.49% <50.00%> (ø)
...xt/assets/doctype/asset_movement/asset_movement.py	77.61% <60.00%> (+4.75%)	⬆️
erpnext/controllers/buying_controller.py	84.66% <66.66%> (ø)
...xt/accounts/doctype/payment_entry/payment_entry.py	83.31% <77.77%> (ø)
...e/subcontracting_receipt/subcontracting_receipt.py	90.25% <85.71%> (ø)
erpnext/accounts/utils.py	73.70% <100.00%> (ø)
erpnext/controllers/sales_and_purchase_return.py	87.38% <100.00%> (ø)
... and 1 more

... and 4 files with indirect coverage changes