distro: rename ListArchs to ListArches

In PR#395 we discussed the spelling of archs vs. arches and we agreed to
use arches. This patch only renames the public method `ListArchs`in the
`Distro` interface.

cmd/osbuild-dnf-json-tests/main_test.go

@@ -61,7 +61,7 @@ func TestCrossArchDepsolve(t *testing.T) {
 			// for the remaining distros
 			continue
 		}
-		for _, archStr := range distroStruct.ListArchs() {
+		for _, archStr := range distroStruct.ListArches() {
 			arch, err := distroStruct.GetArch(archStr)
 			assert.Nilf(t, err, "Failed to GetArch from %v structure: %v", distroStruct.Name(), err)
 			if err != nil {