The Ralts line is only in the Human-Like Egg Group in Gen 8+.
Several other Pokemon had their Egg Group changed in Gen 8 like the Noibat and Trapinch lines added to the Dragon Egg Group, Hawlucha added to the Flying Egg Group, and the Bergmite line added to the Mineral Egg Group, just to name a few. This means that in Gen 5, Gallade can't breed with Pawniard because Gallade is only in the Amorphous Egg Group.
This is information not directly stated on this site, so you would have had to have prior knowledge or checked a different site for knowing. This site does have information on what Pokemon to breed with to get a specific egg move at the bottom of the respective learnset pages, like here and here for example, if that's what you were trying to do.
Hope this helped and good luck breeding!