update actions

Author: singhashmeet

.github/workflows/ci.yml

@@ -14,9 +14,9 @@ jobs:
         java-version: [8, 9, 10, 11]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.1
       - name: Set up JDK ${{ matrix.java-version }}
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v2.3.1
         with:
           java-version: "${{ matrix.java-version }}"
           distribution: "adopt"