`POSITIONAL` holds `name` because `dropIndex` takes it as one. `createIndex`
does not -- it is an option there, and `options()` was stripping it, so a
corpus case asking for a named index silently got a derived one and then
disagreed with an expectation recorded from a driver that had been passed the
name. Two cases in `tests/spec/indexes/partial.json` failed on exactly that.
Put back after the strip rather than removed from the set, because the set is
right for every other operation that reads `args.name`.
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