smoke: remove Rocky Linux 8 from supported OS matrix (#21275)

* smoke: remove Rocky Linux 8 from supported OS matrix

Follow up #21247 by removing Rocky Linux 8 from the smoke OS matrix so smoke tests no longer reference an unavailable AMI.

Co-authored-by: Cursor <cursoragent@cursor.com>
Signed-off-by: Carson Ip <carson.ip@elastic.co>

* smoke: comment out Rocky Linux 8 in OS matrix

Co-authored-by: Cursor <cursoragent@cursor.com>
Signed-off-by: Carson Ip <carson.ip@elastic.co>

---------

Signed-off-by: Carson Ip <carson.ip@elastic.co>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: carsonip

testing/smoke/os_matrix.sh

@@ -8,7 +8,7 @@ os_names=(
     "al2023-ami-2023"
     "RHEL-8"
     "RHEL-9"
-    "Rocky-8-EC2-Base"
+    # "Rocky-8-EC2-Base" # See https://github.com/elastic/apm-server/issues/21179
     "Rocky-9-EC2-Base"
     "AlmaLinux OS 8"
     "AlmaLinux OS 9"