Fix wrong relevancy for libomp tests

libomp is supported in s390x only in Fedora, and if LLVM is 18 or newer
For libomp installed from fedora repos this means Fedora >= 40, for
LLVM snapshots it's enabled always.

tests/libomp/main.fmf

@@ -14,10 +14,16 @@ require+:
   - libomp-devel
 
 adjust+:
-  - because: "libomp is not supported in s390x in 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
 
   # Dependencies in rhel-7 are handled differently: there are no recommends,
   # only requires.

tests/openmp-rpm/main.fmf

@@ -9,9 +9,14 @@ component+:
   - libomp
 
 adjust+:
-  - because: "libomp not supported in s390x"
-    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