OHLC legend precision matches the precision of the rest of the chart

[robustify]

In the commit for the 1.0.16 release (34ce3f7), the precision method of the Chart object was modifed such that the OHLC legend overlay showed prices with the same number of decimal places the user specified in precision.

This functionality regressed with the release of 2.0. Comparing the 1.0.x and 2.x precision methods, I noticed that this line was removed, which is part of the script passed to run_script:

{self.id}.precision = {precision}

This PR simply adds this line back to the script in the precision method. I used the styling example to test. Running it without calling precision uses the default 2 decimal places:

Adding

chart.precision(4)