qa: define centos version for fs:verify

Otherwise it uses the teuthology default of 7.6.

Fixes: https://tracker.ceph.com/issues/43516
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>

diff --git a/qa/suites/fs/verify/centos_latest.yaml b/qa/suites/fs/verify/centos_latest.yaml
new file mode 120000 (symlink)
index 0000000..bd9854e
--- /dev/null
+++ b/qa/suites/fs/verify/centos_latest.yaml
@@ -0,0 +1 @@
+.qa/distros/supported/centos_latest.yaml
\ No newline at end of file