short-term fix of coverage check in CI by removing caching

.github/workflows/coverage.yml

@@ -15,25 +15,7 @@ jobs:
     steps:
       - uses:                   actions/checkout@v2
 
-      ## Cache steps
-
-      - name: Cache cargo registry
-        uses: actions/cache@v1
-        with:
-          path: ~/.cargo/registry
-          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.toml') }}
-
-      - name: Cache cargo index
-        uses: actions/cache@v1
-        with:
-          path: ~/.cargo/git
-          key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.toml') }}
-
-      - name: Cache cargo build
-        uses: actions/cache@v1
-        with:
-          path: target
-          key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.toml') }}
+      # TODO(#315) Re-include caching that also includes the Rust version in the cache key
 
       ## Coverage steps