Fix wrong relevancy for RHEL

tests/main.fmf

@@ -22,10 +22,16 @@ link: []
 tag: []
 
 adjust+:
-  - because: "libomp is not supported in s390x (llvm < 18)"
-    when: >
-      arch == s390x and distro < rhel-9, rhel-9.5, fedora-40, centos-stream-9
+  # Right now libomp in s390x is supported only in LLVM >= 18 in Fedora
+  # TODO until tmt allows to use custom adjusted contexts we need to do this
+  # indirect adjustment using the distro version.
+  - when: arch == s390x and distro < fedora-40 and snapshot is not defined
     enabled: false
+    continue: false
+
+  - when: arch == s390x and distro != fedora
+    enabled: false
+    continue: false
 
   # Common requirements when LLVM is not SCL-ized
   - require+: