Resolve swift warnings that data was never mutated.

[Tanaschita]

No description provided.

[codecov-io]

Codecov Report

Merging #4141 into master will not change coverage.
The diff coverage is 85.71%.

@@           Coverage Diff           @@
##           master    #4141   +/-   ##
=======================================
  Coverage   41.49%   41.49%           
=======================================
  Files         119      119           
  Lines       13995    13995           
=======================================
  Hits         5807     5807           
  Misses       8188     8188

Impacted Files	Coverage Δ
...rce/Charts/Renderers/YAxisRendererRadarChart.swift	0% <0%> (ø)	⬆️
...ce/Charts/Renderers/CandleStickChartRenderer.swift	0% <0%> (ø)	⬆️
Source/Charts/Renderers/LineChartRenderer.swift	65.57% <100%> (ø)	⬆️
Source/Charts/Renderers/PieChartRenderer.swift	68.93% <100%> (ø)	⬆️
.../Charts/Renderers/HorizontalBarChartRenderer.swift	72.24% <100%> (ø)	⬆️
Source/Charts/Renderers/BarChartRenderer.swift	74.61% <100%> (ø)	⬆️
Source/Charts/Renderers/LegendRenderer.swift	61.09% <100%> (ø)	⬆️

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[liuxuan30]

Thanks!
this should be addressed in #4153.