chore(deps): update actions/cache action to v4

.github/workflows/coverage.yml

@@ -21,7 +21,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: ⚡ Cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry

.github/workflows/linux.yml

@@ -23,7 +23,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: ⚡ Cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: |
             /var/lib/docker