fix: don't use generatePermalink in eleventyComputed block

[greatislander]

generatePermalink needs to be used outside of the eleventyComputed block, see Computed data:

It is important to note that Computed Data is computed right before templates are rendered. Therefore Computed Data cannot be used to modify the special data properties used to configure templates (e.g. layout, pagination, tags etc.).

[codecov]

Codecov Report

Merging #201 (69ec0fe) into main (c7403ac) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #201   +/-   ##
=======================================
  Coverage   97.05%   97.05%           
=======================================
  Files          14       14           
  Lines         679      679           
=======================================
  Hits          659      659           
  Misses         20       20           

Files Changed	Coverage Δ
src/utils/generate-permalink.js	100.00% <100.00%> (ø)