Syntax fix: callable type instead of tuple assignment

[mlechu]

Lowering has a bug where an assignment to a where-wrapped tuple is treated like an anonymous function, and it's a very easy typo to make when trying to add a method to a callable type. I found this syntax in two packages, and both seemed to be typos, so this PR corrects the syntax before I make it a proper error. Issue reference: JuliaLang/julia#62051

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.83%. Comparing base (390fd26) to head (f0076c1).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #647      +/-   ##
==========================================
- Coverage   88.09%   87.83%   -0.26%     
==========================================
  Files          29       29              
  Lines        1906     1907       +1     
==========================================
- Hits         1679     1675       -4     
- Misses        227      232       +5     

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[stevengj]

CI failures on nightly seem unrelated (due to Zygote).

[IanButterworth]

Can we get a release? This will trip up pkgeval etc.

[mkitti]

Ok. I will work on a release.

[mkitti]

Released as v0.16.3