maxY value title color is not apply true with opacity color.

**Describe the bug**
Hi, I'm using fl_chart for my app, I faced with color of maxY issue. When I defined leftTitles with text color has opacity, it display maxY wrong color ( still right text style).

**To Reproduce**
This is my code for left side title:
```
leftTitles: AxisTitles(
sideTitles: SideTitles(
showTitles: true,
interval: intervalY == 0 ? 1 : intervalY,
getTitlesWidget: leftTitleWidgets,
reservedSize: 51,
),
),
```
```
Widget leftTitleWidgets(double value, TitleMeta meta) {
return SideTitleWidget(
axisSide: meta.axisSide,
child: Container(
alignment: Alignment.centerRight,
child: Text(
((value - 10) / 1000000000).toStringAsFixed(1),
textAlign: TextAlign.right,
style: ThemeUtils.textStyle.subText
.copyColor(ThemeUtils.color.primary10),
),
),
);
}
```

**Screenshots**

**Versions**
- Flutter version: 3.7.12 stable
- FlChart version: 0.62.0

Please help or notice me if this bug is fixed on new version or whether it is new bug. Thank for advanced! @imaNNeo

Start by reproducing the maxY left-title rendering with the supplied leftTitles, SideTitles, getTitlesWidget, and semi-transparent text style example. Trace how the maxY title is rendered compared with the other titles; done means the configured opacity color is preserved for maxY as well.

Written by the indexing model from the issue text.