ci: update rust-cache action to fix security vuln (#15)

Author: disrupted

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
 
       - name: Cache cargo
         if: startsWith(github.ref, 'refs/tags/') != true
-        uses: Swatinem/rust-cache@v1
+        uses: Swatinem/rust-cache@v2
 
       - name: Build debug
         if: matrix.config.kind == 'test_debug'