fix: set limit correctly in batcher queries

[erizocosmico]

Limit was only being applied per batch, not globally, because of which the batcher retrieved all rows in the database.

[codecov-io]

Codecov Report

Merging #109 into master will increase coverage by 0.04%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #109      +/-   ##
==========================================
+ Coverage   80.81%   80.86%   +0.04%     
==========================================
  Files          15       15              
  Lines        2685     2691       +6     
==========================================
+ Hits         2170     2176       +6     
  Misses        351      351              
  Partials      164      164

Impacted Files	Coverage Δ
batcher.go	78.94% <77.77%> (+1.16%)	✅

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