Switch docker image from :doxygen1.8.15 to :master

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   build:
     docker:
-      - image: djarek/boost_superproject_build:doxygen1.8.15
+      - image: djarek/boost_superproject_build:master
     parallelism: 2
     steps:
       - checkout