fix model printing

[GiggleLiu]

I notice that there are some printing issue is the current documentation. Which will be fixed by this PR. I also removed the nclique field of the UAIModel type, which is not used anywhere in the code.

Before the fix

The variables are not shown

After the fix

julia> using TensorInference

julia> model = read_model_file(pkgdir(TensorInference, "examples", "asia", "asia.uai"))
UAIModel(nvars = 8, nfactors = 8
 cards : [2, 2, 2, 2, 2, 2, 2, 2]
 factors : 
  Factor(1), size = (2,)
  Factor(1, 2), size = (2, 2)
  Factor(3), size = (2,)
  Factor(3, 4), size = (2, 2)
  Factor(3, 5), size = (2, 2)
  Factor(2, 4, 6), size = (2, 2, 2)
  Factor(6, 7), size = (2, 2)
  Factor(5, 6, 8), size = (2, 2, 2)

[codecov[bot]]

Codecov Report

Merging #53 (1e4bacf) into main (79797ea) will increase coverage by 0.51%. The diff coverage is 82.22%.

@@            Coverage Diff             @@
##             main      #53      +/-   ##
==========================================
+ Coverage   81.07%   81.59%   +0.51%     
==========================================
  Files           9        9              
  Lines         502      489      -13     
==========================================
- Hits          407      399       -8     
+ Misses         95       90       -5     

Impacted Files	Coverage Δ
src/TensorInference.jl	100.00% <ø> (+25.00%)	:arrow_up:
src/Core.jl	46.29% <22.22%> (-7.23%)	:arrow_down:
src/mmap.jl	71.18% <86.66%> (ø)
src/map.jl	100.00% <100.00%> (ø)
src/mar.jl	94.64% <100.00%> (ø)
src/sampling.jl	98.75% <100.00%> (ø)
src/utils.jl	89.68% <100.00%> (+0.42%)	:arrow_up: