allow in/out contract expressions in shortened methods

[WebFreak001]

Fixes contract expressions with shortened methods introduced in the previous PR #439

Might want to improve syntax errors with it, but this should work for now.

[codecov]

Codecov Report

Merging #454 (df248d4) into master (413a416) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #454      +/-   ##
==========================================
+ Coverage   82.79%   82.82%   +0.02%     
==========================================
  Files          11       11              
  Lines        8290     8301      +11     
==========================================
+ Hits         6864     6875      +11     
  Misses       1426     1426              

Impacted Files	Coverage Δ
src/dparse/ast.d	70.25% <ø> (ø)
src/dparse/parser.d	91.26% <100.00%> (+0.02%)	⬆️

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[WebFreak001]

note: errors like `do` expected after InStatement or OutStatement seem to never be emitted. Unsure if this is because of this PR, though they aren't tested anyway. Might want to add error message tests in the future and improve some areas (like the fail file in fail_files/shortenedMethod.d as well)