Fix multiple primary keys results in syntax error (duplicate "NOT NULL")

[soryy708]

Pull Request check-list

Please make sure to review and check all of these items:

• [V] Does npm run test or npm run test-DIALECT pass with this change (including linting)?
• [V] Does the description below contain a link to an existing issue (Closes #[issue]) or a description of the issue you are solving?
• [V] Have you added new tests to prevent regressions?
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Description of change

Fixes #12194

[codecov]

Codecov Report

Merging #12237 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master   #12237   +/-   ##
=======================================
  Coverage   96.33%   96.33%           
=======================================
  Files          95       95           
  Lines        9118     9120    +2     
=======================================
+ Hits         8784     8786    +2     
  Misses        334      334           

Impacted Files	Coverage Δ
lib/dialects/sqlite/query-generator.js	96.63% <100.00%> (+0.03%)	⬆️

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[soryy708]

@sushantdhiman When will a version of sequelize be published that includes this bugfix?
Would you agree that being unable to make a composite key out of a column that has a "not null" constraint (what this PR fixed) is a critical bug?

[sushantdhiman]

@soryy708 Master branch is currently tracking v6 beta, I am not sure when next beta release will be shipped.

If you want this in v5 stable release, please submit this PR for v5 branch. It will get auto released upon merge :)