Switch pre-update index to FR4 for minor update job

Updates minor update edpm job to use FR4 pre-update index
for initial deploy and then updates it to main with PR.

Signed-off-by: rabi <[email protected]>

Author: rabi

zuul.d/edpm.yaml

@@ -57,7 +57,7 @@
       crc_parameters: "--memory 32000 --disk-size 240 --cpus 12"
       cifmw_manage_secrets_pullsecret_content: '{}'
       cifmw_rhol_crc_binary_folder: "/usr/local/bin"
-      cifmw_minor_update_pre_update_tag: "18.0-fr3-latest"
+      cifmw_minor_update_pre_update_tag: "18.0-fr4-latest"
 
 # Podified galera job
 - job: