Fix Zygote pullback depwarning

[mhauru]

Zygote kept saying this:

┌ Warning: Incorrect argument order for pullback, please use:
│ 
│   pullback(f, __context__::Context, args)
│ 
│ instead of:
│ 
│   pullback(__context__::Context, f, args)
│ 
│ This is usually caused by a call to pullback in a higher-order @adjoint.
│ The above warning will become an error in Zygote 0.7.
└ @ Zygote ~/.julia/packages/Zygote/nsBv0/src/compiler/interface.jl:95

[github-actions]

Pull Request Test Coverage Report for Build 10777382418

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.6%) to 75.952%

---

Totals
Change from base Build 10701838580:	-1.6%
Covered Lines:	2672
Relevant Lines:	3518

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 10777382418

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 77.508%

---

Totals
Change from base Build 10701838580:	0.0%
Covered Lines:	2712
Relevant Lines:	3499

---

💛 - Coveralls

[yebai]

Thanks @mhauru!