Update the documentation about GPU support

[amontoison]

CuArrays.jl is deprecated.

[coveralls]

Coverage decreased (-0.2%) to 97.424% when pulling 98af001 on amontoison:gpu into dc68bfa on JuliaSmoothOptimizers:master.

[codecov]

Codecov Report

Merging #216 into master will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #216      +/-   ##
==========================================
- Coverage   97.46%   97.39%   -0.07%     
==========================================
  Files          30       30              
  Lines        3233     3190      -43     
==========================================
- Hits         3151     3107      -44     
- Misses         82       83       +1     

Impacted Files	Coverage Δ
src/diom.jl	92.94% <0.00%> (-1.25%)	⬇️
src/cr.jl	57.23% <0.00%> (-0.27%)	⬇️
src/krylov_utils.jl	95.45% <0.00%> (-0.20%)	⬇️
src/craig.jl	96.72% <0.00%> (-0.03%)	⬇️
src/symmlq.jl	97.81% <0.00%> (-0.02%)	⬇️
src/cg.jl	100.00% <0.00%> (ø)
src/cgs.jl	100.00% <0.00%> (ø)
src/qmr.jl	100.00% <0.00%> (ø)
src/bilq.jl	100.00% <0.00%> (ø)
src/cgls.jl	100.00% <0.00%> (ø)
... and 20 more

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[dpo]

Thank you.