Fix dark mode for line color in Charts
Summary:
Colors of lines and areas in Charts cannot be "fixed" for dark mode by introducing more variables to the Celerity Postprocessor as their colors are not defined via CSS classes but in PHP.
Thus change the dark blue line `rgba(0, 0, 200, 1)` displayed on top of `$lightbluebackground` (`#F8F9FC` in default mode, and problematic `rgba(255,255,255,.05)` in dark mode) to `rgba(41, 128, 185, 1)` which works reasonably well in both default and dark mode.
Refs T15056
Test Plan:
* Enable the "Facts" application at http://phorge.localhost/applications/view/PhabricatorFactApplication/
* Go to http://phorge.localhost/project/reports/1/ and look at the line and its area in the chart
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T15056
Differential Revision: https://we.phorge.it/D26237