bug: fix using 'none' for chart legend position in configs

[ClementTsang]

Description

A description of the change, what it does, and why it was made. If relevant (such as any change that modifies the UI), please provide screenshots of the changes:

Parse "none" when checking legend position in configs. This was being done in args but not config for whatever reason.

Issue

If applicable, what issue does this address?

Closes: #1591

Testing

If relevant, please state how this was tested. All changes must be tested to work:

If this is a code change, please also indicate which platforms were tested:

• Windows
• macOS
• Linux

Checklist

If relevant, ensure the following have been met:

• Areas your change affects have been linted using rustfmt (cargo fmt)
• The change has been tested and doesn't appear to cause any unintended breakage
• Documentation has been added/updated if needed (README.md, help menu, doc pages, etc.)
• The pull request passes the provided CI pipeline
• There are no merge conflicts
• If relevant, new tests were added (don't worry too much about coverage)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 41.86%. Comparing base (35a7eca) to head (2f806b9).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/options.rs	0.00%	8 Missing ⚠️
src/canvas/components/tui_widget/time_chart.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1593      +/-   ##
==========================================
- Coverage   41.86%   41.86%   -0.01%     
==========================================
  Files         114      114              
  Lines       17668    17672       +4     
==========================================
+ Hits         7397     7398       +1     
- Misses      10271    10274       +3     

Flag	Coverage Δ
macos-12	37.27% <0.00%> (-0.01%)	⬇️
ubuntu-latest	43.62% <0.00%> (-0.01%)	⬇️
windows-2019	37.22% <0.00%> (-0.01%)	⬇️

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