Remove support for opensuse

We haven't been testing the distro for a while in CI, e.g. in
Tempest, the jobs on opensuse15 haven't been executed for a year
now.
Therefore the patch removes opensuse support from devstack.

Closes-Bug: #2002900
Change-Id: I0f5e4c644e2d14d1b8bb5bc0096d1469febe5fcc
diff --git a/doc/source/index.rst b/doc/source/index.rst
index 1e932f8..ccd0fef 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -38,8 +38,7 @@
 
 Start with a clean and minimal install of a Linux system. DevStack
 attempts to support the two latest LTS releases of Ubuntu, the
-latest/current Fedora version, CentOS/RHEL/Rocky Linux 9, OpenSUSE and
-openEuler.
+latest/current Fedora version, CentOS/RHEL/Rocky Linux 9 and openEuler.
 
 If you do not have a preference, Ubuntu 22.04 (Jammy) is the
 most tested, and will probably go the smoothest.