Disable jobs that should be disabled.

Signed-off-by: Arthur She <arthur.she@linaro.org>
Change-Id: I7b219f4267f33ab9222727c151190f0f2c34014a
diff --git a/mbed-tls-pr-merge.yaml b/mbed-tls-pr-merge.yaml
index c031f19..8de2cab 100644
--- a/mbed-tls-pr-merge.yaml
+++ b/mbed-tls-pr-merge.yaml
@@ -2,6 +2,7 @@
     name: mbed-tls-pr-merge
     description: 'Job for testing PRs merged with the target branch head'
     project-type: multibranch
+    disabled: true
     prune-dead-branches: true
     days-to-keep: 60
     num-to-keep: 1000