Merge pull request #6774 from tureba/patch-2

edb_otel: add requirement on EPEL for RHEL 9

Author: nidhibhammar

advocacy_docs/pg_extensions/otel/installing.mdx

@@ -26,6 +26,11 @@ Before you begin the installation process:
 
   To set up the repository, go to [EDB repositories](https://www.enterprisedb.com/repos-downloads) and follow the instructions provided there.
 
+  If you are using RHEL 9, you also need to install the EPEL repository:
+  ```shell
+  sudo dnf -y install https://dl.fedoraproject.org/pub/epel/epel-release-latest-9.noarch.rpm
+  ```
+
 
 ### Install the package