Treatment of `length` is inconsistent in 9.4.2 and 9.4.3

[rkirsling]

• 9.4.2 has a long first paragraph describing the length property:

  Every Array object has a length property ...

  Yet it also has the following sentence dangling as its own paragraph afterwards:

  Array exotic objects always have a non-configurable property named "length".

  Seems like the latter should be deleted and the word "non-configurable" added to the former.

• 9.4.3 exclusively uses "length" in its exposition:

  String exotic objects always have a data property named "length" ... Both the code unit data properties and the "length" property ...

  This is locally consistent, but I think it could be changed to just length for consistency with 9.4.2.

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Note: The string "length" is used for good reason in the algorithmic steps; this issue is purely about the explanatory text.

[ljharb]

Seems fine.

[ljharb]

Seems fine.