Removed unnecessary test that fails with iris 3.4.0

[schlunma]

Description

This PR removes a test that fails after a bugfix that has been introduced with iris 3.4.0 (SciTools/iris#5062). The tests that check that dtype is preserved are now located in iris and can be removed from our test suite.

Checklist

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[codecov]

Codecov Report

Merging #1846 (6be241a) into main (5107f12) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1846   +/-   ##
=======================================
  Coverage   91.54%   91.54%           
=======================================
  Files         203      203           
  Lines       10945    10945           
=======================================
  Hits        10020    10020           
  Misses        925      925           

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[schlunma]

The test coverage will be restored when fixing #1802 (but we need an iris>=3.4.0 pin for that one).

[bouweandela]

Thanks for taking care of this!

[valeriupredoi]

thanks a lot, Manu! 🍺