fix: hsn-wise summary is incorrect if an invoice has repeated item code

[nextchamp-saqib]

HSN Wise summary report shows incorrect data If a Sales Invoice has some item repeated more than once with a different rate/quantity and GST is applied on these items

To verify the fix:

• Create a Sales Invoice with an item having some HSN code set. Duplicate the item 2-3 times.
• Apply GST on these items
• Submit the Invoice
• Go to the HSN Wise summary report and set HSN Code and Date filters to query only the created invoice.
• The taxable value should match the total amount of all the items

[codecov]

Codecov Report

Merging #28783 (6a239c8) into develop (ef53eb7) will increase coverage by 0.31%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop   #28783      +/-   ##
===========================================
+ Coverage    55.27%   55.58%   +0.31%     
===========================================
  Files         1122     1125       +3     
  Lines        66772    66971     +199     
===========================================
+ Hits         36906    37224     +318     
+ Misses       29866    29747     -119     

Impacted Files	Coverage Δ
...d_supplies/hsn_wise_summary_of_outward_supplies.py	72.38% <ø> (+72.38%)	⬆️
...ctype/woocommerce_settings/woocommerce_settings.py	80.00% <0.00%> (-4.00%)	⬇️
erpnext/education/doctype/student/student.py	73.68% <0.00%> (-3.16%)	⬇️
...nts/doctype/accounts_settings/accounts_settings.py	97.50% <0.00%> (-2.50%)	⬇️
...ion/doctype/course_enrollment/course_enrollment.py	44.00% <0.00%> (-2.00%)	⬇️
.../report/stock_projected_qty/stock_projected_qty.py	86.84% <0.00%> (-1.32%)	⬇️
erpnext/stock/stock_ledger.py	85.56% <0.00%> (-0.61%)	⬇️
erpnext/accounts/deferred_revenue.py	75.43% <0.00%> (-0.57%)	⬇️
.../report/accounts_receivable/accounts_receivable.py	68.37% <0.00%> (-0.43%)	⬇️
erpnext/support/doctype/issue/issue.py	64.03% <0.00%> (-0.36%)	⬇️
... and 37 more