Remove text colors

[gsalinas]

Removed the colors from the Base.show() implementation for ModbusContexts so they display properly regardless of terminal color schemes, usage in logs, etc.

Thanks!

[kagalenko-m-b]

The test fails when run in github cloud. I was unable to determine the reason. It passed when unit_test_client.jl had been run against unit-test-server from libmobus. Fixing this would be quite helpful, but if you can't figure out what is going on, probably best to leave it unchanged by this PR.

[gsalinas]

Gotcha! Unfortunate. I've reverted the change to the test for now.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.46 🎉

Comparison is base (e66cbb3) 76.06% compared to head (95e476d) 76.52%.

❗ Current head 95e476d differs from pull request most recent head 69d82a3. Consider uploading reports for the commit 69d82a3 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master       #3      +/-   ##
==========================================
+ Coverage   76.06%   76.52%   +0.46%     
==========================================
  Files           1        1              
  Lines         330      328       -2     
==========================================
  Hits          251      251              
+ Misses         79       77       -2     

Impacted Files	Coverage Δ
src/LibModbus.jl	76.52% <0.00%> (+0.46%)	⬆️

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[kagalenko-m-b]

Thanks, merged the changes.