use stable version of docker image

Qinghao Shi · Qinghao Shi · commit 60ca96e97e38 · 2019-12-31T14:26:55.000Z
diff --git a/.circleci/config.yml b/.circleci/config.yml
@@ -6,7 +6,7 @@ version: 2
 jobs:
   build:
     docker:
-      - image: mbedos/mbed-os-env:latest
+      - image: mbedos/mbed-os-env:stable
     working_directory: ~/repo
     steps:
       - checkout:
