Remove interpolate tests when mir is not linked

[MircoValentiniECMWF]

Description

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌈🌦️📖🚧 Documentation 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/dev-section/multio/pull-requests/PR-278

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 33.21%. Comparing base (def29f1) to head (ae9105b).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #278   +/-   ##
========================================
  Coverage    33.21%   33.21%           
========================================
  Files          374      374           
  Lines        41061    41061           
  Branches      1703     1703           
========================================
  Hits         13637    13637           
  Misses       27424    27424           

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