docs: clarify DataArray coords list description

[jaythehardcoder]

Description

Closes #10118.

Clarifies the DataArray user-guide description of coords when a list is passed. The old text said a list "should be a list of tuples", but the example immediately below uses coords=[times, locs] with dims=["time", "space"]. The updated text matches that positional form and points readers to dictionaries for named or more complex coordinate definitions.

Checklist

• Closes Description of coords type in documentation contradicts the example following it. #10118
• Tests added
• User visible changes (including notable bug fixes) are documented in whats-new.rst
• New functions/methods are listed in api.rst

Verification

• Ran a Python check for the documented xr.DataArray(data, coords=[times, locs], dims=["time", "space"]) example and verified the dimensions/coordinates.
• Checked that the stale "list of tuples" wording was removed from doc/user-guide/data-structures.rst.

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