ci-linux: Remove unmaintained local-conda runs (#35125)
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### 📚 Description
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These are jobs that run directly on the GH Actions container instead of
using Docker.
We remove them.
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These jobs have been failing for a long time.
Newer tests for conda-forge have been added in `ci-conda.yml`, which
makes these ones here obsolete.
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### ⌛ Dependencies
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