Disable pr-merge automatic triggers

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
Change-Id: I44a2e41ca003224e60f783a32d4dd7793a079afc
diff --git a/mbed-tls-pr-merge.yaml b/mbed-tls-pr-merge.yaml
index c031f19..3e73477 100644
--- a/mbed-tls-pr-merge.yaml
+++ b/mbed-tls-pr-merge.yaml
@@ -39,6 +39,9 @@
         discover-pr-forks-trust: permission
         discover-pr-origin: both
         head-filter-regex: '(?!^PR-(1824)-(merge|head)$)(PR-\d+-merge)'
+        property-strategies:
+          all-branches:
+          - suppress-scm-triggering: true
         submodule:
           disable: false
           recursive: true