FIX: 1225 horizontal lines not rendering at max and min

[JoshMart]

This fixes #1255 where extra horizontal lines would not be painted when they were to be drawn horizontally along the min or max of the chart.

[codecov]

Codecov Report

Merging #1266 (f09d739) into master (122c6e3) will increase coverage by 0.02%.
The diff coverage is 38.29%.

@@            Coverage Diff             @@
##           master    #1266      +/-   ##
==========================================
+ Coverage   85.94%   85.97%   +0.02%     
==========================================
  Files          45       45              
  Lines        2945     2951       +6     
==========================================
+ Hits         2531     2537       +6     
  Misses        414      414              

Impacted Files	Coverage Δ
.../src/chart/base/axis_chart/axis_chart_painter.dart	71.98% <38.29%> (+0.83%)	⬆️

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[imaNNeo]

We have this logic in BarChart too. Please check and fix it if there is any bug in the BarChart.
Thanks!

[imaNNeo]

BTW everything looks good to me.
Please fix the codecov issue, then we are ready to merge it.

[JoshMart]

BTW everything looks good to me. Please fix the codecov issue, then we are ready to merge it.

codecov/patch is reporting uncovered lines on code that existed before this PR. The lines in question were simply indented because they are now wrapped in an if block. They are not new.