Update of swapAnimationDuration and swapAnimationCurve in docs

[SantiiRepair]

Update of swapAnimationDuration and swapAnimationCurve in markdown files due to current deprecation.

[imaNNeo]

Oh, I just realized that we updated line_chart properties by mistake (in this commit):

fl_chart/lib/src/chart/line_chart/line_chart.dart

Lines 18 to 19 in 4a2924a

	super.duration = const Duration(milliseconds: 150),
	super.curve = Curves.linear,

Now we just need to rename it back to swapAnimationDuration and swapAnimationCurve just like other charts:

fl_chart/lib/src/chart/bar_chart/bar_chart.dart

Lines 17 to 18 in 4a2924a

	Duration swapAnimationDuration = const Duration(milliseconds: 150),
	Curve swapAnimationCurve = Curves.linear,

fl_chart/lib/src/chart/pie_chart/pie_chart.dart

Lines 15 to 16 in 4a2924a

	Duration swapAnimationDuration = defaultDuration,
	Curve swapAnimationCurve = Curves.linear,

[SantiiRepair]

there are no conflicts with the base branch now

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c911024) 86.73% compared to head (34297a4) 86.73%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1496   +/-   ##
=======================================
  Coverage   86.73%   86.73%           
=======================================
  Files          45       45           
  Lines        3022     3022           
=======================================
  Hits         2621     2621           
  Misses        401      401           

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[imaNNeo]

It has conflicts again. Sorry for my delay.

[SantiiRepair]

haha I won't solve anything, it took you 2 months to remember this pull request.

[imaNNeo]

I try my best to keep it updated and work on it, but as you might know, my time is limited just like everyone.
And keep in mind that no one hired me to work on this library and as a result, it is free for everyone.
Thanks for your effort btw.