DX-914: Don't set `:site_destination_dir`

[asbjornu]

Setting :site_destination_dir here may cause the following error if the options_hash is nil:

undefined method `[]=' for nil:NilClass (NoMethodError)

[codecov[bot]]

Codecov Report

Merging #75 (61524d6) into main (b92939b) will decrease coverage by 0.01%. The diff coverage is n/a.

:exclamation: Current head 61524d6 differs from pull request most recent head 550ff71. Consider uploading reports for the commit 550ff71 to get more accurate results

@@            Coverage Diff             @@
##             main      #75      +/-   ##
==========================================
- Coverage   94.03%   94.01%   -0.02%     
==========================================
  Files          12       12              
  Lines         419      418       -1     
==========================================
- Hits          394      393       -1     
  Misses         25       25              

Impacted Files	Coverage Δ
lib/kramdown-plantuml/jekyll_provider.rb	86.11% <ø> (-0.20%)	:arrow_down:

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[mergify[bot]]

Thank you @asbjornu for your contribution!