Temporary skip decimal256 integration tests

[jorgecarleitao]

We do not support it but they are being run on the arrow's test suite.

See #1194, that adds support.

[codecov]

Codecov Report

Merging #1198 (71e9a24) into main (9f6be52) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1198      +/-   ##
==========================================
- Coverage   83.52%   83.52%   -0.01%     
==========================================
  Files         364      364              
  Lines       36398    36398              
==========================================
- Hits        30403    30402       -1     
- Misses       5995     5996       +1     

Impacted Files	Coverage Δ
src/io/ipc/read/array/boolean.rs	90.74% <0.00%> (-7.41%)	⬇️
src/io/ipc/read/reader.rs	96.32% <0.00%> (-0.34%)	⬇️
src/array/utf8/mod.rs	83.64% <0.00%> (+0.92%)	⬆️
src/bitmap/utils/slice_iterator.rs	98.78% <0.00%> (+1.21%)	⬆️

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