fix: Unable to delete selected rows in some input tables

[mofojed]

• Erroneously assumed that the key columns were the first columns in the table
• Removed unused delete function from IrisGridTableModelTemplate
  • It should only be implemented for regular JsTables as JsTreeTables do not have input tables
  • Was duplicated code
• Fixes Unable to delete rows in input tables when key columns are not the first columns #1677
• Tested using the code in the ticket

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (1b06675) 46.63% compared to head (0e443fb) 46.68%.

Files	Patch %	Lines
packages/iris-grid/src/IrisGridTableModel.ts	0.00%	7 Missing ⚠️
...ckages/iris-grid/src/IrisGridTableModelTemplate.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1678      +/-   ##
==========================================
+ Coverage   46.63%   46.68%   +0.05%     
==========================================
  Files         604      604              
  Lines       36753    36711      -42     
  Branches     9211     9206       -5     
==========================================
  Hits        17139    17139              
+ Misses      19562    19520      -42     
  Partials       52       52              

Flag	Coverage Δ
unit	46.68% <0.00%> (+0.05%)	⬆️

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