fix!: drop old broken demo files

[ankush]

Dropping support for make-demo command; this hasn't worked properly for a long time now. If you ask me the main reason is schema/code for demo gets out of sync with other changes and that makes it unusable after few such breakages. Whoever wants to fix this make a separate app and ensure that it runs in CI else it will face the same fate again.

Technically a breaking change; but is it breaking if it wasn't working? :thonk:

[codecov]

Codecov Report

Merging #29339 (93fd7bd) into develop (fabe0bc) will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop   #29339      +/-   ##
===========================================
+ Coverage    57.93%   57.95%   +0.01%     
===========================================
  Files         1110     1110              
  Lines        68091    68065      -26     
===========================================
- Hits         39450    39444       -6     
+ Misses       28641    28621      -20     

Impacted Files	Coverage Δ
erpnext/commands/__init__.py	0.00% <0.00%> (ø)
...eport/item_variant_details/item_variant_details.py	31.32% <0.00%> (-56.63%)	⬇️
...tch_item_expiry_status/batch_item_expiry_status.py	69.23% <0.00%> (-25.00%)	⬇️
...wise_balance_history/batch_wise_balance_history.py	68.96% <0.00%> (-24.14%)	⬇️
.../report/bom_operations_time/bom_operations_time.py	93.33% <0.00%> (-3.34%)	⬇️
...xt/stock/report/stock_analytics/stock_analytics.py	91.08% <0.00%> (-1.99%)	⬇️
...eorder_level/itemwise_recommended_reorder_level.py	92.45% <0.00%> (-1.89%)	⬇️
erpnext/stock/report/stock_ledger/stock_ledger.py	76.42% <0.00%> (-1.63%)	⬇️
erpnext/stock/report/stock_ageing/stock_ageing.py	92.48% <0.00%> (-1.16%)	⬇️
erpnext/selling/doctype/sales_order/sales_order.py	77.29% <0.00%> (-0.77%)	⬇️
... and 21 more