qa/upgrade: drop broken symlink

octopus-only: this change was introduced in: c2486c7239f2efff1f87a0c6064ccbf792e90bf0
as a linking unintentional typo while creating symlink, the parent
commit was octopus only hence we don't require it in other branches.

Signed-off-by: Deepika Upadhyay <dupadhya@redhat.com>

diff --git a/qa/suites/upgrade/mimic-x/stress-split- b/qa/suites/upgrade/mimic-x/stress-split-
deleted file mode 120000 (symlink)
index 324f99c..0000000
--- a/qa/suites/upgrade/mimic-x/stress-split-
+++ /dev/null
@@ -1 +0,0 @@
-qa/distros/supported-random-distro$/ubuntu_18.04.yaml
\ No newline at end of file