[repository] Drop the index on entities.type It should be now only used in maintenance queries in checkintegrity. Those are not worth maintaining it. Closes #15538317

Release notes
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.. toctree::
    :maxdepth: 1

    3.23
    3.22
    3.21
    3.20
    3.19
    3.18
    3.17
    3.16
    3.15
    3.14