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

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
Change-Id: I5fef990f17333507c2e9d1ac73ead5941520764b
diff --git a/mbed-tls-restricted-pr-test-parametrized.yaml b/mbed-tls-restricted-pr-test-parametrized.yaml
index 6d2b377..6c8ddfb 100644
--- a/mbed-tls-restricted-pr-test-parametrized.yaml
+++ b/mbed-tls-restricted-pr-test-parametrized.yaml
@@ -109,7 +109,7 @@
         description: Branch or tag in https://github.com/Mbed-TLS/mbedtls-test.git (forks are not supported)
         type: PT_BRANCH_TAG
         quickFilterEnabled: True
-        defaultValue: master
+        defaultValue: main
     pipeline-scm:
       lightweight-checkout: false
       scm: