Run i386 tests on debian instead of ubuntu

It appears Ubuntu has pulled their 18.04LTS i386 images (and they don't have more recent i386 images), so we need to switch to Debian instead.

Author: Leont

.github/workflows/testsuite.yml

@@ -304,15 +304,15 @@ jobs:
   # |_|_|_| |_|\__,_/_/\_\    |_|____/ \___/ \___/
 
   linux-i386:
-    name: "linux i386/ubuntu"
-    runs-on: ubuntu-latest
+    name: "linux i386/debian"
+    runs-on: debian-latest
     timeout-minutes: 120
     needs: sanity_check
     if: (! cancelled() && (needs.sanity_check.outputs.run_all_jobs == 'true' || needs.sanity_check.outputs.ci_force_linux_i386 == 'true'))
 
-    # https://hub.docker.com/r/i386/ubuntu/
+    # https://hub.docker.com/r/i386/debian/
     container:
-      image: i386/ubuntu:latest
+      image: i386/debian:latest
 
     strategy:
       fail-fast: false