8313701: GHA: RISC-V should use the official repository for bootstrap

Reviewed-by: phh
Backport-of: 538f9557b87f750264231f04bfbc91d15f8af8c0

Author: shipilev

.github/workflows/build-cross-compile.yml

@@ -86,7 +86,7 @@ jobs:
           - target-cpu: riscv64
             gnu-arch: riscv64
             debian-arch: riscv64
-            debian-repository: https://deb.debian.org/debian-ports
+            debian-repository: https://httpredir.debian.org/debian/
             debian-version: sid
 
     steps: