ci/debian-build-testing: drop extra nesting section

`.gitlab-ci/meson/build.sh` already prints sections, having an extra one
here just means that nothing is visible by default.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29113>

.gitlab-ci/build/gitlab-ci.yml

@@ -190,7 +190,7 @@ debian-build-testing:
     .gitlab-ci/run-shellcheck.sh
     section_switch yamllint "yamllint"
     .gitlab-ci/run-yamllint.sh
-    section_switch meson "meson"
+    section_end
     .gitlab-ci/meson/build.sh
     .gitlab-ci/prepare-artifacts.sh
   timeout: 15m