Update JLCPCB gerber settings according to their recommendation

[kinoshita-lab]

Since I have been making PCBs with former setting and there have been no problems so far, some settings for JLCPCB(and its with-stencil version) do not match their recommendation written by JLCPCB itself: https://support.jlcpcb.com/article/149-how-to-generate-gerber-and-drill-files-in-kicad

This pull request corrects the settings below:

• File name extension(they prefer Protel's)
• Drill file settings

I have also confirmed they have started production with updated settings.

[g200kg]

Thank you!