tests: CRB in CentOS has different name

tests/build-gating.fmf

@@ -24,6 +24,15 @@ adjust:
       WITH_SCL: "scl enable llvm-toolset-13.0 rust-toolset-1.58"
     when: "collection == llvm-toolset-13.0"
 
+  # Unfortunatelly, TMT does not support more declarative approach, we need to run commands on our own.
+  - because: "On CentOS, CRB must be enabled to provide rarer packages"
+    prepare+:
+      - name: Enable CRB
+        how: shell
+        script: dnf config-manager --set-enabled crb
+    when: >-
+      distro == centos
+
   # Unfortunatelly, TMT does not support more declarative approach, we need to run commands on our own.
   - because: "On RHEL, CRB must be enabled to provide rarer packages"
     prepare+:
@@ -31,8 +40,7 @@ adjust:
         how: shell
         script: dnf config-manager --set-enabled rhel-CRB
     when: >-
-      distro == centos
-      or distro == rhel-9
+      distro == rhel-9
       or distro == rhel-8
 
   # Unfortunatelly, TMT does not support more declarative approach, we need to run commands on our own.