Update checkout action to v2

Author: riccardobl

.github/workflows/main.yml

@@ -66,7 +66,7 @@ jobs:
 
     steps:
       - name: Clone the repo
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2     
         with:
           fetch-depth: 1
       - name: Validate the Gradle wrapper
@@ -94,7 +94,7 @@ jobs:
 
     steps:
       - name: Clone the repo
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2     
         with:
           fetch-depth: 1
       - name: Validate the Gradle wrapper
@@ -131,7 +131,7 @@ jobs:
     steps:
 
       - name: Clone the repo
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2     
         with:
           fetch-depth: 1
 
@@ -197,7 +197,7 @@ jobs:
 
     steps:
       - name: Clone the repo
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
         with:
           fetch-depth: 1
 
@@ -406,7 +406,7 @@ jobs:
 
       # We need to clone everything again for uploadToMaven.sh ...
       - name: Clone the repo
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
         with:
           fetch-depth: 1