Rename mbedtls-test branch "master" to "main"

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
Change-Id: I5fef990f17333507c2e9d1ac73ead5941520764b
diff --git a/mbedtls-restricted-release-new.yaml b/mbedtls-restricted-release-new.yaml
index 9275378..794e5bf 100644
--- a/mbedtls-restricted-release-new.yaml
+++ b/mbedtls-restricted-release-new.yaml
@@ -111,7 +111,7 @@
       scm:
       - git:
           branches:
-          - 'master'
+          - main
           url: https://github.com/Mbed-TLS/mbedtls-test.git
       script-path: vars/mbedtls-release-Jenkinsfile
     project-type: pipeline