chore: use develop for core tests

Author: tamtamchik

.github/workflows/core_tests.yml

@@ -36,7 +36,7 @@ jobs:
       - name: Run init script
         run: docker exec -e CORE_BRANCH tests-runner bash -c 'PYTHONPATH=$PWD make init'
         env:
-          CORE_BRANCH: master
+          CORE_BRANCH: develop
 
       - name: Run node
         run: docker exec -e ETH_RPC_URL --detach tests-runner bash -c 'NODE_PORT=8545 make node'