chore: Build UBI 15 versions for ppc64le s390x

Signed-off-by: Jonathan Gonzalez V <jonathan.gonzalez@enterprisedb.com>

.github/generate-strategy.sh

@@ -115,7 +115,7 @@ for version in "${ubi_versions[@]}"; do
 		fullVersion="${fullVersion%[.-]*}"
 	done
 
-	if [[ "${version}" =~ ^("15")$ ]]; then
+	if [[ "${version}" =~ ^("16")$ ]]; then
 			platforms="linux/amd64"
 	else
 			platforms="linux/amd64, linux/ppc64le, linux/s390x, linux/arm64"