fix: subtract change_amount from paid_amount field on POS Register

[HarryPaulo]

When a sale is made and the difference amount is not allocated as change.

Example 1:
Sales: $9.90
Client pays $10 and receives change.
Change Amout: $0.1
Write Off Amout: $0

Report before my change show:
grand_total: $9.90
paid_amount: $10

With my change, show de real paid amout like show on pos close entry:
grand_total: $9.90
paid_amount: $9.90

Example 2:
Sales: $9.90
Customer pays $10 and will not receive change.
Change Amout: 0
Write Off Amout: $0.1

Rerpot before my change and with my changes show:
grand_total: $9.90
paid_amount: $10

With this we will have the real value received!

[codecov]

Codecov Report

Merging #30922 (f5e11e4) into develop (dafdc9b) will increase coverage by 1.30%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop   #30922      +/-   ##
===========================================
+ Coverage    61.77%   63.08%   +1.30%     
===========================================
  Files         1079      983      -96     
  Lines        69701    67062    -2639     
===========================================
- Hits         43057    42305     -752     
+ Misses       26644    24757    -1887     

Impacted Files	Coverage Δ
...pnext/accounts/report/pos_register/pos_register.py	0.00% <ø> (ø)
...xt/hr/doctype/employee_checkin/employee_checkin.py	94.26% <100.00%> (+0.62%)	⬆️
erpnext/hr/doctype/shift_type/shift_type.py	86.41% <100.00%> (+0.34%)	⬆️
erpnext/domains/retail.py	0.00% <0.00%> (-100.00%)	⬇️
erpnext/domains/services.py	0.00% <0.00%> (-100.00%)	⬇️
erpnext/domains/distribution.py	0.00% <0.00%> (-100.00%)	⬇️
erpnext/domains/manufacturing.py	0.00% <0.00%> (-100.00%)	⬇️
..._integrations/connectors/woocommerce_connection.py	0.00% <0.00%> (-77.09%)	⬇️
...ctype/woocommerce_settings/woocommerce_settings.py	28.84% <0.00%> (-55.77%)	⬇️
...rial_no_valuation/incorrect_serial_no_valuation.py	85.96% <0.00%> (-10.53%)	⬇️
... and 155 more