Automatic update from web-platform-testsCorrect serialization of background-color (#9499)
According to https://drafts.csswg.org/css-color/#resolving-color-values, transparent should serialize to "rgba(0, 0, 0, 0)", and named colors should serialize to their equivalent value in rgb notation. Change the expectations for 3 background tests in order to match this part of the spec.
wpt-commits: 43deb07215d283d63e2bdca51d6268eba43bbe81
wpt-pr: 9499
wpt-commits: 43deb07215d283d63e2bdca51d6268eba43bbe81
wpt-pr: 9499