Add defer to PostRun function

[kaduartur]

- What I did
I added a defer statement to PostRun

- How to verify it
Run a formula and check the .rit folder, thetmp directory must not exist!

- Description for the changelog
Remove tmp directory to not fill the user's disk

[codecov-commenter]

Codecov Report

Merging #548 into master will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #548      +/-   ##
==========================================
+ Coverage   78.54%   78.58%   +0.03%     
==========================================
  Files          98       98              
  Lines        3179     3184       +5     
==========================================
+ Hits         2497     2502       +5     
  Misses        498      498              
  Partials      184      184              

Impacted Files	Coverage Δ
pkg/formula/runner/docker/runner.go	92.30% <100.00%> (+0.30%)	⬆️
pkg/formula/runner/local/runner.go	94.59% <100.00%> (+0.30%)	⬆️
pkg/formula/runner/post_run.go	100.00% <100.00%> (ø)

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[brunasilvazup]

LGTM

[kaduartur]

/merge qa

[ritchie-bot]

👌 Merged branch fix/remove_tmp_dir into qa