Improve theme-color-level() using abs() (#24074)
Improve theme-color-level() using abs() (#24074)

`abs()` gets the absolute value of `$level`.
That way, `if/else` statement can be completely eliminated.
zalog/bootstrap,creativewebjp/bootstrap,tagliala/bootstrap,Lyricalz/bootstrap,9-chirno/chirno,fschumann1211/bootstrap,janseliger/bootstrap,SweetProcess/bootstrap,stanwmusic/bootstrap,nice-fungal/bootstrap,tibo66/bootstrap,9-chirno/chirno,m5o/bootstrap,lipis/bootstrap,gijsbotje/bootstrap,nice-fungal/bootstrap,bootstrapbrasil/bootstrap,tagliala/bootstrap,kvlsrg/bootstrap,yuyokk/bootstrap,TheFridayInstitute/bootstrap,vsn4ik/bootstrap,twbs/bootstrap,joblocal/bootstrap,Delagen/bootstrap,vsn4ik/bootstrap,realcrowd/bootstrap,fschumann1211/bootstrap,jipexu/bootstrap,bardiharborow/bootstrap,GerHobbelt/bootstrap,jipexu/bootstrap,kvlsrg/bootstrap,creativewebjp/bootstrap,realcrowd/bootstrap,stanwmusic/bootstrap,zalog/bootstrap,bardiharborow/bootstrap,inway/bootstrap,Hemphill/bootstrap-docs,coliff/bootstrap,tibo66/bootstrap,stanwmusic/bootstrap,inway/bootstrap,kvlsrg/bootstrap,janseliger/bootstrap,janseliger/bootstrap,GerHobbelt/bootstrap,coliff/bootstrap,TheFridayInstitute/bootstrap,tibo66/bootstrap,m5o/bootstrap,bootstrapbrasil/bootstrap,supergibbs/bootstrap,gijsbotje/bootstrap,tjkohli/bootstrap,SweetProcess/bootstrap,fschumann1211/bootstrap,Delagen/bootstrap,Delagen/bootstrap,seanwu99/bootstrap,creativewebjp/bootstrap,stanwmusic/bootstrap,supergibbs/bootstrap,supergibbs/bootstrap,joblocal/bootstrap,9-chirno/chirno,realcrowd/bootstrap,realcrowd/bootstrap,tibo66/bootstrap,tjkohli/bootstrap,Lyricalz/bootstrap,yuyokk/bootstrap,seanwu99/bootstrap,creativewebjp/bootstrap,joblocal/bootstrap,twbs/bootstrap,SweetProcess/bootstrap,joblocal/bootstrap,SweetProcess/bootstrap,Delagen/bootstrap,GerHobbelt/bootstrap,janseliger/bootstrap,inway/bootstrap,seanwu99/bootstrap,bardiharborow/bootstrap,zalog/bootstrap,peterblazejewicz/bootstrap,TheFridayInstitute/bootstrap,vsn4ik/bootstrap,gijsbotje/bootstrap,seanwu99/bootstrap,jipexu/bootstrap,supergibbs/bootstrap,fschumann1211/bootstrap,TheFridayInstitute/bootstrap,Hemphill/bootstrap-docs,Hemphill/bootstrap-docs,lipis/bootstrap,vsn4ik/bootstrap,9-chirno/chirno,tagliala/bootstrap,Lyricalz/bootstrap,yuyokk/bootstrap,nice-fungal/bootstrap,Hemphill/bootstrap-docs,gijsbotje/bootstrap,lipis/bootstrap,peterblazejewicz/bootstrap,Lyricalz/bootstrap,lipis/bootstrap,peterblazejewicz/bootstrap,jipexu/bootstrap,bootstrapbrasil/bootstrap,yuyokk/bootstrap,bardiharborow/bootstrap