Fix config not loaded when using --config

[bhirsz]

Fixes #138

[codecov-commenter]

Codecov Report

Merging #139 (f62e2df) into main (5c50daa) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #139      +/-   ##
==========================================
- Coverage   97.09%   97.08%   -0.01%     
==========================================
  Files          24       24              
  Lines        1274     1271       -3     
==========================================
- Hits         1237     1234       -3     
  Misses         37       37              

Impacted Files	Coverage Δ
robotidy/cli.py	93.66% <100.00%> (-0.14%)	⬇️

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