Arthur: Change to mbedtls-github-token

arthur-mbed-tls-pr-head.yaml
arthur-mbed-tls-pr-merge.yaml

Signed-off-by: Arthur She <arthur.she@linaro.org>
Change-Id: I36c66ccfb7ab0a033d75a88e6f594073395d77b3
diff --git a/arthur-mbed-tls-pr-head.yaml b/arthur-mbed-tls-pr-head.yaml
index c5c0abf..8bf970a 100644
--- a/arthur-mbed-tls-pr-head.yaml
+++ b/arthur-mbed-tls-pr-head.yaml
@@ -30,7 +30,7 @@
     scm:
     - github:
         api-uri: https://api.github.com
-        credentials-id: arthur-mbedtls-github-token
+        credentials-id: mbedtls-github-token
         repo-owner: arthur-she
         repo: mbedtls
         repository-url: https://github.com/arthur-she/mbedtls.git