ci: update actions to pinned SHA numbers

.github/dependabot.yml

@@ -0,0 +1,7 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    open-pull-requests-limit: 10

.github/workflows/testnet-build.yml

@@ -17,12 +17,12 @@ jobs:
     # 1 - checkout project and dependencies
 
     - name: Checkout Phoenix
-      uses: actions/checkout@v2
+      uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       with:
         path: phoenix
 
     - name: Checkout lightning-kmp
-      uses: actions/checkout@v2
+      uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       with:
         repository: ACINQ/lightning-kmp
         ref: master
@@ -31,14 +31,14 @@ jobs:
     # 2 - setup cache/jdk
 
     - name: Cached Konan
-      uses: actions/cache@v4
+      uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4.2.3
       with:
         path: ~/.konan
         key: ${{ runner.os }}-konan-${{ hashFiles('**/*.gradle*') }}-${{ hashFiles('**/gradle/wrapper/gradle-wrapper.properties') }}
         restore-keys: ${{ runner.os }}-konan-
 
     - name: Set up jdk 1.17
-      uses: actions/setup-java@v1
+      uses: actions/setup-java@b6e674f4b717d7b0ae3baee0fbe79f498905dfde # v1.4.4
       with:
         java-version: 17
 
@@ -78,7 +78,7 @@ jobs:
       # 5 - upload apk
 
     - name: Upload apk as artifact for this action
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
       with:
         name: phoenix-testnet
         path: upload/phoenix-testnet-latest.apk