Update Oracle Linux and Enterprise Linux references to 9+ to align with RHEL9+ requirement

- Updated Oracle Linux 6+/7+ references to Oracle Linux 9+ in software-hardware-requirements.rst
- Updated Enterprise Linux 7+ and Oracle Linux 6+/7+ references to Enterprise Linux 9+ and Oracle Linux 9+ in deploy-rhel.rst
- Updated desktop app RHEL/CentOS 7+ reference to RHEL/CentOS 9+ for consistency

Co-authored-by: Carrie Warner (Mattermost) <cwarnermm@users.noreply.github.com>

Author: claude[bot]

source/deploy/server/linux/deploy-rhel.rst

@@ -7,7 +7,7 @@
     <div class="mm-badge__reqs">
       <h3>Minimum system requirements:</h3>
       <ul>
-        <li>Operating System: Enterprise Linux 7+, Oracle Linux  6+, Oracle Linux 7+</li>
+        <li>Operating System: Enterprise Linux 9+, Oracle Linux 9+</li>
         <li>Hardware: 1 vCPU/core with 2GB RAM (support for up to 1,000 users)</li>
         <li>Database: <a href="https://docs.mattermost.com/deploy/postgres-migration.html">PostgreSQL v13+</a></li>
         <li>Network:

source/deploy/software-hardware-requirements.rst

@@ -27,7 +27,7 @@ Desktop apps
     "Mac", "macOS 12+", "macOS 12+"
     "Linux", "Ubuntu LTS releases 22.04 or later", "Ubuntu LTS releases 22.04 or later"
 
-Though not officially supported, the Linux desktop app also runs on RHEL/CentOS 7+.
+Though not officially supported, the Linux desktop app also runs on RHEL/CentOS 9+.
 
 .. note::
 
@@ -84,7 +84,7 @@ Server software
 Mattermost server operating system
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-- Ubuntu, Debian Buster, CentOS 6+, CentOS 7+, RedHat Enterprise Linux 9+, Oracle Linux 6+, Oracle Linux 7+.
+- Ubuntu, Debian Buster, CentOS 6+, CentOS 7+, RedHat Enterprise Linux 9+, Oracle Linux 9+.
 - Using the Mattermost `Docker deployment <https://github.com/mattermost/docker>`__ on a Docker-compatible operating system (Linux-based OS) is still recommended.
 
 .. important::