Revert "set 2020 in license src so that syntax text do not complain"
Revert "set 2020 in license src so that syntax text do not complain"

This reverts commit 96376e87bb8f5eb8959c64ec1a87fd0d82f91a3c.

plotly/plotly.js,plotly/plotly.js,plotly/plotly.js,plotly/plotly.js