Update GHA cache version

Author: emilyploszaj

.github/workflows/build.yml

@@ -17,7 +17,7 @@ jobs:
         with:
           java-version: ${{ matrix.java }}
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: |
             ~/.gradle/caches

.github/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           java-version: ${{ matrix.java }}
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: |
             ~/.gradle/caches