Remove pocl-related tests

pocl has been FTBFS since Fedora 38. There is a plan to orphan it.

tests/build-gating-pocl.fmf

@@ -1,34 +0,0 @@
-summary: PoCL clang tests for build/PR gating
-adjust:
-  - because: "Plan to be ran when either executed locally, or executed by CI system to gate a build or PR."
-    when: >-
-      trigger is defined
-      and trigger != commit
-      and trigger != build
-    enabled: false
-
-  - because: "PoCL is shipped with Fedora, not RHEL/CentOS"
-    when: >-
-      distro == rhel
-      or distro == centos
-    enabled: false
-
-discover:
-    how: fmf
-    test: pocl
-    url: https://src.fedoraproject.org/tests/clang.git
-    ref: main
-execute:
-    how: tmt
-prepare:
-    # Programs linked against pocl should be able to run without clang installed,
-    # so when we run the test we want to make sure clang is not installed to
-    # verify we haven't introduced an implicit dependency on clang.
-    - name: Drop clang
-      how: shell
-      script: |
-        dnf erase -y clang
-
-provision:
-  hardware:
-    memory: ">= 4 GiB"