Fix OutOfMemoryError in test

[jishnub]

Not entirely sure if the array indices were chosen to satisfy any specific condition, but if they weren't then tests need not create such large arrays.

Previously

julia> y = OffsetArray{Float64}(undef, -1:1, -7:7, -128:512, -5:5, -1:1, -3:3, -2:2, -1:1);

julia> Base.summarysize(y)/2^20 # size in MB
762.5423049926758

Now

julia> y = OffsetArray{Float64}(undef, -1:1, -7:7, -1:2, -5:5, -1:1, -3:3, -2:2, -1:1);

julia> Base.summarysize(y)/2^20
4.75860595703125

This was leading to occasional OutOfMemoryErrors while testing locally.

[codecov]

Codecov Report

Merging #154 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #154   +/-   ##
=======================================
  Coverage   94.02%   94.02%           
=======================================
  Files           2        2           
  Lines         251      251           
=======================================
  Hits          236      236           
  Misses         15       15           

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