feat: Remove css custom properties for absolute colors

To use absolute colors, it's best to rely on
stylus/settings/palette.json. Most of the time though, you'll want to
use css custom properties for theme (var(--primaryColor),
var(--secondaryColor) for example).

BREAKING CHANGE: Some CSS custom variables for colors have been removed,
you are encouraged to import directly the colors from
cozy-ui/stylus/settings/palette if necessary.

Here is the list of colors that have been removed:

    --hawkesBlue   #EEF5FE
    --frenchPass   #C2DCFF
    --azure        #1FA8F1
    --puertoRico   #0DCBCF
    --grannyApple  #DEF7E7
    --seafoamGreen #3DA67E
    --brightSun      #FFC644
    --texasRose      #FFAE5F
    --pumpkinOrange  #FF7F1B
    --blazeOrange    #FC6D00
    --melon          #FD7461
    --lavender        #C2ADF4
    --darkPeriwinkle  #6984CE
    --purpley         #7F6BEE
    --portage         #9169F2
    --lightishPurple  #B449E7
    --barney          #922BC2

stylus/settings/palette.styl

@@ -56,56 +56,34 @@ html
     Blue
 
     Stylus: zircon       -  #F5FAFF, CSS: var(--zircon)
-    Stylus: hawkesBlue   -  #EEF5FE, CSS: var(--hawkesBlue)
-    Stylus: frenchPass   -  #C2DCFF, CSS: var(--frenchPass)
-    Stylus: azure        -  #1FA8F1, CSS: var(--azure)
     Stylus: dodgerBlue   -  #297EF2, CSS: var(--dodgerBlue)
     Stylus: scienceBlue  -  #0B61D6, CSS: var(--scienceBlue)
-    Stylus: puertoRico   -  #0DCBCF, CSS: var(--puertoRico)
 
     Styleguide Settings.colors.blue
     */
     --zircon       #F5FAFF
-    --hawkesBlue   #EEF5FE
-    --frenchPass   #C2DCFF
-    --azure        #1FA8F1
     --dodgerBlue   #297EF2
     --scienceBlue  #0B61D6
-    --puertoRico   #0DCBCF
     /*
     Green
 
-    Stylus: grannyApple  - #DEF7E7, CSS: var(--grannyApple)
     Stylus: weirdGreen   - #40DE8E, CSS: var(--weirdGreen)
     Stylus: emerald      - #35CE68, CSS: var(--emerald)
     Stylus: malachite    - #08b442, CSS: var(--malachite)
-    Stylus: seafoamGreen - #3DA67E, CSS: var(--seafoamGreen)
 
     Styleguide Settings.colors.green
     */
-    --grannyApple  #DEF7E7
     --weirdGreen   #40DE8E
     --emerald      #35CE68
     --malachite    #08b442
-    --seafoamGreen #3DA67E
     /*
     Orange
 
-    Stylus: brightSun     - #FFC644, CSS: var(--brightSun)
-    Stylus: texasRose     - #FFAE5F, CSS: var(--texasRose)
     Stylus: mango         - #FF962F, CSS: var(--mango)
-    Stylus: pumpkinOrange - #FF7F1B, CSS: var(--pumpkinOrange)
-    Stylus: blazeOrange   - #FC6D00, CSS: var(--blazeOrange)
-    Stylus: melon         - #FD7461, CSS: var(--melon)
 
     Styleguide Settings.colors.orange
     */
-    --brightSun      #FFC644
-    --texasRose      #FFAE5F
     --mango          #FF962F
-    --pumpkinOrange  #FF7F1B
-    --blazeOrange    #FC6D00
-    --melon          #FD7461
     /*
     Red
 
@@ -122,25 +100,6 @@ html
     --fuchsia      #FC4C83
     --pomegranate  #F52D2D
     --monza        #DD0505
-    /*
-    Purple
-
-    Stylus: lavender       - #C2ADF4, CSS: var(--lavender)
-    Stylus: darkPeriwinkle - #6984CE, CSS: var(--darkPeriwinkle)
-    Stylus: purpley        - #7F6BEE, CSS: var(--purpley)
-    Stylus: portage        - #9169F2, CSS: var(--portage)
-    Stylus: lightishPurple - #B449E7, CSS: var(--lightishPurple)
-    Stylus: barney         - #922BC2, CSS: var(--barney)
-
-    Styleguide Settings.colors.purple
-    */
-    --lavender        #C2ADF4
-    --darkPeriwinkle  #6984CE
-    --purpley         #7F6BEE
-    --portage         #9169F2
-    --lightishPurple  #B449E7
-    --barney          #922BC2
-
     /*
         Theme