Merge pull request #627 from dfinity/andriy/update-periodic-tasks

Update `README` and `Cargo.toml` in `periodic-tasks`

Author: dfinity-berestovskyy

.github/workflows/rust-periodic_tasks-example.yaml

@@ -18,6 +18,8 @@ jobs:
     steps:
       - uses: actions/checkout@v1
       - name: Provision Darwin
+        env:
+          DFX_VERSION: 0.13.1
         run: bash .github/workflows/provision-darwin.sh
       - name: Rust Periodic Tasks Darwin
         run: |
@@ -30,6 +32,8 @@ jobs:
     steps:
       - uses: actions/checkout@v1
       - name: Provision Linux
+        env:
+          DFX_VERSION: 0.13.1
         run: bash .github/workflows/provision-linux.sh
       - name: Rust Periodic Tasks Linux
         run: |