Fix GitHub Actions: Update actions/cache from v1 to v4

- Update actions/cache@v1 to actions/cache@v4 in UnitTest.yml
- Update actions/cache@v1 to actions/cache@v4 in documentation.yml
- Fixes deprecation warning that was causing CI failures

Author: ibrahim Al-Aqua

.github/workflows/UnitTest.yml

@@ -25,7 +25,7 @@ jobs:
           version: ${{ matrix.julia-version }}
 
       - name: Cache artifacts
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         env:
           cache-name: cache-artifacts
         with:

.github/workflows/documentation.yml

@@ -23,7 +23,7 @@ jobs:
         with:
           version: ${{ matrix.julia-version }}
       - name: Cache artifacts
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         env:
           cache-name: cache-artifacts
         with: