fix: threshold fields shows incorrect currency

[nextchamp-saqib]

In case the Tax Withholding Category is not created for the same region as Company's country, the currency fields shows Company's currency which is incorrect.

For eg. for a US-based company if a user creates a Tax Withholding Category for India, then the Threshold fields show $ symbols

Fix:
Convert Currency fields to Float

[codecov]

Codecov Report

Merging #29270 (0e1b832) into develop (75c8b25) will increase coverage by 0.14%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop   #29270      +/-   ##
===========================================
+ Coverage    57.73%   57.87%   +0.14%     
===========================================
  Files         1110     1110              
  Lines        67992    68005      +13     
===========================================
+ Hits         39258    39361     +103     
+ Misses       28734    28644      -90     

Impacted Files	Coverage Δ
erpnext/manufacturing/doctype/bom/bom.py	86.76% <ø> (-0.09%)	⬇️
...ext/accounts/report/balance_sheet/balance_sheet.py	36.36% <0.00%> (-21.82%)	⬇️
...ucation/doctype/course_schedule/course_schedule.py	83.33% <0.00%> (-13.22%)	⬇️
erpnext/stock/reorder_item.py	75.21% <0.00%> (-1.71%)	⬇️
...cial_statement/consolidated_financial_statement.py	88.81% <0.00%> (-0.96%)	⬇️
erpnext/accounts/deferred_revenue.py	75.87% <0.00%> (-0.88%)	⬇️
...rpnext/stock/report/stock_balance/stock_balance.py	79.16% <0.00%> (-0.60%)	⬇️
...evenue_and_expense/deferred_revenue_and_expense.py	61.30% <0.00%> (-0.31%)	⬇️
...stock/doctype/purchase_receipt/purchase_receipt.py	90.42% <0.00%> (-0.27%)	⬇️
.../report/accounts_receivable/accounts_receivable.py	71.36% <0.00%> (-0.22%)	⬇️
... and 28 more