Move passes-related settings outside _create_params

[osma]

So they don't confuse model loading. Without this fix, annif eval seems to hang.
#230

[codecov]

Codecov Report

Merging #253 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #253      +/-   ##
=========================================
+ Coverage    99.3%   99.3%   +<.01%     
=========================================
  Files          51      51              
  Lines        2431    2432       +1     
=========================================
+ Hits         2414    2415       +1     
  Misses         17      17

Impacted Files	Coverage Δ
annif/backend/vw_multi.py	100% <100%> (ø)	⬆️
tests/test_backend_vw.py	100% <100%> (ø)	⬆️

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