Don't use rules for UniformScaling on 1.0

[mcabbott]

#533 enforces that I is its own tangent. Since this package still allows Julia 1.0, and the current ChainRules does not, this apparently breaks DistributionsAD on Julia 1.5.

This PR is one way to avoid that. It would need to be in one release before dropping 1.0 forever.

However, since there has been exactly one release with #533 in it (list https://github.com/JuliaDiff/ChainRulesCore.jl/releases/) the alternative would just be to edit one line in the registry to make that release 1.6-only. And make all new releases here 1.6 only too, which we should probably do in any case.

You could also mess with releases on multiple branches, but that sounds harder.

[github-actions]

[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

	(pr::ProjectTo{UniformScaling})(dx::Tangent{<:UniformScaling}) = UniformScaling(pr.λ(dx.λ))
	function (pr::ProjectTo{UniformScaling})(dx::Tangent{<:UniformScaling})
	return UniformScaling(pr.λ(dx.λ))
	end

[codecov-commenter]

Codecov Report

Merging #542 (de84f62) into main (3394de6) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #542   +/-   ##
=======================================
  Coverage   93.41%   93.41%           
=======================================
  Files          15       15           
  Lines         866      866           
=======================================
  Hits          809      809           
  Misses         57       57           

Impacted Files	Coverage Δ
src/projection.jl	97.30% <100.00%> (ø)

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[mzgubic]

You could also mess with releases on multiple branches, but that sounds harder.

Why is it harder? Can we not just register a tag from a branch?

If we merge this PR, and then bump the compat to 1.6 we have to at that point undo the changes this PR introduced.

[oxinabox]

Suggested change

	# but shouldn't on Julia 1.0, as rules in CR.jl were added only after mioving to 1.6
	# but shouldn't on Julia 1.0, as rules in CR.jl were added only after moving to 1.6

[oxinabox]

@mzgubic do you think we should just go and backport the missing rules into CR and tag a backported release?

[mzgubic]

Yes, I can do that. Let's merge #544 and I will backport JuliaDiff/ChainRules.jl#571 to ChainRules 1.21, as it was before https://github.com/JuliaDiff/ChainRules.jl/pull/577/files