ci/build: drop mold wrapper for ninja install

`install` doesn't perform any linking, it just installs what we built in
the previous command.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32046>

.gitlab-ci/meson/build.sh

@@ -170,10 +170,6 @@ fi
 uncollapsed_section_switch meson-test "meson: test"
 LC_ALL=C.UTF-8 meson test --num-processes "${FDO_CI_CONCURRENT:-4}" --print-errorlogs ${MESON_TEST_ARGS}
 section_switch meson-install "meson: install"
-if command -V mold &> /dev/null ; then
-    mold --run ninja install
-else
-    ninja install
-fi
+ninja install
 cd ..
 section_end meson-install