changed parsing logic; only try to get encoding if initial parsing fails

[fpgmaas]

PR Checklist

• A description of the changes is added to the description of this PR.
• If there is a related issue, make sure it is linked to this PR.
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

Description of changes

[codecov-commenter]

Codecov Report

Merging #105 (567a435) into main (004d780) will decrease coverage by 0.2%.
The diff coverage is 83.3%.

@@           Coverage Diff           @@
##            main    #105     +/-   ##
=======================================
- Coverage   94.7%   94.5%   -0.3%     
=======================================
  Files         30      30             
  Lines       1120    1132     +12     
=======================================
+ Hits        1061    1070      +9     
- Misses        59      62      +3     

Impacted Files	Coverage Δ
deptry/import_parser.py	93.4% <81.2%> (-2.8%)	⬇️
tests/test_import_parser.py	100.0% <100.0%> (ø)

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[fpgmaas]

#102