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

Reviewed-by: clanger, fyang

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

@@ -86,8 +86,7 @@ jobs:
           - target-cpu: riscv64
             gnu-arch: riscv64
             debian-arch: riscv64
-            debian-repository: https://deb.debian.org/debian-ports
-            debian-keyring: /usr/share/keyrings/debian-ports-archive-keyring.gpg
+            debian-repository: https://httpredir.debian.org/debian/
             debian-version: sid
 
     steps: