ci: replace with amazonlinux2 container image

Using vagrant for AmazonLinux 2 is troublesome to spin up
AL2 VM frequently. It tend to stall network stack.

Instead, directly specify jobs.job_id.container.image.
It avoid issues run CGroup v1 container (AL2) on CGroup
v2 host (ubuntu-latest).

Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>

Author: kenhys

.github/workflows/yum.yml

@@ -189,6 +189,8 @@ jobs:
     # approach. Instead, use vagrant on Ubuntu 24.04.
     # (NOTE: nested VM is executable on macos-13, but it is too slow)
     runs-on: ubuntu-24.04
+    container:
+      image: docker.io/amazonlinux:2
     timeout-minutes: 15
     strategy:
       fail-fast: false