upgrade/dumpling-x: do not do ec test on mixed cluster

dumpling doens't support it

Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/suites/upgrade/dumpling-x/stress-split/9-workload/ec-rados-plugin=jerasure-k=2-m=1.yaml b/suites/upgrade/dumpling-x/stress-split/9-workload/ec-rados-plugin=jerasure-k=2-m=1.yaml
deleted file mode 120000 (symlink)
index 4baff9b..0000000
--- a/suites/upgrade/dumpling-x/stress-split/9-workload/ec-rados-plugin=jerasure-k=2-m=1.yaml
+++ /dev/null
@@ -1 +0,0 @@
-../../../../../erasure-code/ec-rados-plugin=jerasure-k=2-m=1.yaml
\ No newline at end of file