chore: replace term_size with terminal_size

[pamburus]

Reason: RUSTSEC-2020-0163.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 84.28%. Comparing base (274d968) to head (5869cb4).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/help.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1014   +/-   ##
=======================================
  Coverage   84.28%   84.28%           
=======================================
  Files          47       47           
  Lines       13025    13029    +4     
=======================================
+ Hits        10978    10982    +4     
  Misses       2047     2047           

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