chore: remove vmkeeper.maxcycles

[moul]

Let's remove the vn.maxCycles variable from the VM keeper so that it relies solely on the built-in gas system.

maxCycles remains an option on gno.Machine for blockchainless and gasless experiences.

[codecov]

Codecov Report

Attention: Patch coverage is 64.00000% with 18 lines in your changes missing coverage. Please review.

Project coverage is 63.13%. Comparing base (88a0c4e) to head (2519add).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
gno.land/pkg/sdk/vm/keeper.go	60.86%	18 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2993      +/-   ##
==========================================
+ Coverage   63.11%   63.13%   +0.02%     
==========================================
  Files         563      563              
  Lines       79284    79274      -10     
==========================================
+ Hits        50041    50051      +10     
+ Misses      25871    25853      -18     
+ Partials     3372     3370       -2     

Flag	Coverage Δ
contribs/gnodev	60.57% <100.00%> (-0.05%)	⬇️
contribs/gnofaucet	15.77% <ø> (+0.94%)	⬆️
gno.land	67.38% <61.70%> (+0.01%)	⬆️
gnovm	67.26% <ø> (ø)
misc/genstd	79.72% <ø> (ø)
tm2	62.39% <ø> (+0.13%)	⬆️

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