chore(dev/release): duplicate, not overwrite, yum repo

[lidavidm]

https://github.com/apache/arrow-adbc/actions/runs/29970729853/job/89092001443

  Last metadata expiration check: 0:01:05 ago on Thu Jul 23 01:08:48 2026.
  Error: 
   Problem: package adbc-arrow-glib-devel-24-1.el9.x86_64 from apache-arrow-almalinux requires libadbc-arrow-glib.so.1()(64bit), but none of the providers can be installed
    - package adbc-arrow-glib-devel-24-1.el9.x86_64 from apache-arrow-almalinux requires adbc-arrow-glib1-libs = 24-1.el9, but none of the providers can be installed
    - conflicting requests
    - nothing provides libarrow-glib.so.2500()(64bit) needed by adbc-arrow-glib1-libs-24-1.el9.x86_64 from apache-arrow-almalinux
  (try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

I'm not sure how this worked before, but this changes the verification script to add the ADBC Yum repo as an additional repo instead of overwriting the Arrow one.

Generated-by: GPT 5.6 Sol codex@openai.com

[lidavidm]

https://github.com/lidavidm/arrow-adbc/actions/runs/29973681858

[lidavidm]

Looks like this does fix the verification run.