Fix #rrggbbaa color to rgba for better browser compatibility

[SagePtr]

Fixes #4988

Color format #rrggbbaa is not widely supported by browsers yet: https://caniuse.com/#search=rgba
Less fade function is better here as it generates rgba(r, g, b, a) format output which has much better browser support. Also Less <3.8.1 handles #rrggbbaa format wrong as pointed in #4988 issue.

[codecov-io]

Codecov Report

Merging #4990 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #4990      +/-   ##
=========================================
- Coverage    37.4%   37.4%   -0.01%     
=========================================
  Files         306     306              
  Lines       45373   45373              
=========================================
- Hits        16974   16972       -2     
- Misses      25945   25948       +3     
+ Partials     2454    2453       -1

Impacted Files	Coverage Δ
modules/process/manager.go	76.81% <0%> (-4.35%)	⬇️
models/repo_list.go	61.76% <0%> (-1.18%)	⬇️
models/repo_indexer.go	52.11% <0%> (+1.27%)	⬆️

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[techknowlogick]

Maintainer note: This doesn't have a milestone applied to it. I'd like it to be in 1.6, but we should wait for #4971 to get merged first before merging this as the other PR already had to resolve conflicts arising from other CSS changes. I don't want to have the other contributor to have to resolve the same conflicts again.

That being said, I am only one of many maintainers and so if someone has a different opinion that is fine too.

[lafriks]

Please rebase and resolve conflicts

[SagePtr]

Done it and regenerated stylesheet