[cli] adds empty line for help command

[damirka]

Closes #362

Details:

• clap 2.X has an issue with adding empty line in the end
• proper fixing of this problem should be by updating to V3

Resources:

• 2018 issue with code example: Using -? for help in addition to -h clap-rs/clap#1127 (comment)
• https://gitmemory.com/issue/clap-rs/clap/1536/534784807

[codecov]

Codecov Report

Merging #565 (fd952b8) into master (1a36a26) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #565      +/-   ##
==========================================
+ Coverage   74.57%   74.61%   +0.04%     
==========================================
  Files         472      472              
  Lines       13929    13932       +3     
==========================================
+ Hits        10387    10396       +9     
+ Misses       3542     3536       -6     

Impacted Files	Coverage Δ
leo/main.rs	100.00% <ø> (ø)
compiler/src/expression/arithmetic/pow.rs	0.00% <0.00%> (-27.78%)	⬇️
core/src/types/core_package.rs	75.00% <0.00%> (-1.93%)	⬇️
type-inference/src/objects/frame.rs	93.71% <0.00%> (-0.40%)	⬇️
grammar/src/ast.rs	94.38% <0.00%> (ø)
ast/src/expression/mod.rs	85.46% <0.00%> (ø)
ast/src/expression/binary.rs	83.33% <0.00%> (ø)
compiler/src/expression/expression.rs	95.83% <0.00%> (ø)
compiler/src/value/integer/integer.rs	94.57% <0.00%> (ø)
compiler/tests/integers/uint_macro.rs	96.70% <0.00%> (ø)
... and 6 more

---

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[acoglio]

Looks good to me, thanks.