docs: typo in associations.md

[ggarek]

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Description of change

Probably, wrong property was being used in the docs example. This PR fixes this typo.

Looks like the last example should define association rather then model in this case.

Using model the error happens:

Error: Unable to connect to the database TypeError: self._expandAttributes is not a function
    at Function._conformOptions (<...>/node_modules/sequelize/lib/model.js:198:12)
    at Function._conformInclude (<...>/node_modules/sequelize/lib/model.js:264:12)
    at options.include.options.include.map.include (<...>/node_modules/sequelize/lib/model.js:213:59)
    at Array.map (<anonymous>)
    at Function._conformOptions (<...>/node_modules/sequelize/lib/model.js:213:39)
    at new Model (<...>/node_modules/sequelize/lib/model.js:3070:24)
    at new jp_kanji (<...>/node_modules/sequelize/lib/sequelize.js:340:19)
    at Function.build (<...>/node_modules/sequelize/lib/model.js:1966:12)
    at Function.create (<...>/node_modules/sequelize/lib/model.js:2017:17)
    <client code>

[codecov]

Codecov Report

Merging #10157 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #10157   +/-   ##
=======================================
  Coverage   96.35%   96.35%           
=======================================
  Files          63       63           
  Lines        9426     9426           
=======================================
  Hits         9082     9082           
  Misses        344      344

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[sushantdhiman]

Thanks @ggarek