feat: use an ubuntu based image for manylinux_2_31_riscv64

This allows wider compatibility than manylinux_2_39

Author: mayeut

pyproject.toml

@@ -100,7 +100,7 @@ manylinux-aarch64-image = "manylinux2014"
 manylinux-ppc64le-image = "manylinux2014"
 manylinux-s390x-image = "manylinux2014"
 manylinux-armv7l-image = "manylinux_2_31"
-manylinux-riscv64-image = "manylinux_2_39"
+manylinux-riscv64-image = "ghcr.io/mayeut/manylinux_2_31:2025.08.02-2"
 musllinux-x86_64-image = "quay.io/pypa/musllinux_1_1_x86_64:2024.10.26-1"
 musllinux-i686-image = "quay.io/pypa/musllinux_1_1_i686:2024.10.26-1"
 musllinux-aarch64-image = "quay.io/pypa/musllinux_1_1_aarch64:2024.10.26-1"