upgrade to actions/cache@v4

Author: testforstephen

.github/workflows/build.yml

@@ -20,7 +20,7 @@ jobs:
         java-version: '21'
 
     - name: Cache local Maven repository
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
@@ -51,7 +51,7 @@ jobs:
         java-version: '21'
 
     - name: Cache local Maven repository
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: $HOME/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
@@ -77,7 +77,7 @@ jobs:
         java-version: '21'
 
     - name: Cache local Maven repository
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}