gitlab-ci.yml: use $CI_DEFAULT_BRANCH instead of main

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

.gitlab-ci.yml

@@ -85,4 +85,4 @@ deploy:
         echo "Nothing new to commit.";
       fi
   rules:
-    - if: '$CI_COMMIT_BRANCH == "main"'
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'