chore(app): remove old upgrade handlers logic

[GAtom22]

Description

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Closes #XXX

[MalteHerrmann]

I think we need the second to last upgrade information for the upgrade tests. IIRC that logic looks for the available upgrade folders and uses the second to last one as the default initial version for the upgrade

[codecov]

Codecov Report

Merging #2139 (233c22c) into main (f179530) will increase coverage by 0.55%.
Report is 3 commits behind head on main.
The diff coverage is 87.87%.

❗ Current head 233c22c differs from pull request most recent head 2f45129. Consider uploading reports for the commit 2f45129 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2139      +/-   ##
==========================================
+ Coverage   69.10%   69.65%   +0.55%     
==========================================
  Files         304      294      -10     
  Lines       23737    23126     -611     
==========================================
- Hits        16403    16108     -295     
+ Misses       6433     6151     -282     
+ Partials      901      867      -34     

Files	Coverage Δ
app/app.go	80.90% <100.00%> (+1.39%)	⬆️
precompiles/staking/types.go	87.33% <100.00%> (-0.12%)	⬇️
precompiles/staking/tx.go	88.37% <80.00%> (-0.05%)	⬇️
precompiles/staking/events.go	72.36% <81.25%> (+1.26%)	⬆️

... and 1 file with indirect coverage changes