Both the definition and implementation of the != operator have been removed from the RGBColor class because C++20 automatically generates the != operator from the == operator. Change-Id: Ia84fa254d1d11d127f55b79f213eb64789269c7d Reviewed-on: https://gerrit.libreoffice.org/c/core/+/206183 Tested-by: Jenkins Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>