fix: install cargo-llvm-cov when not present in cache (#782)

The cargo cache that is setup for the coverage job is also caching
cargo-llvm-cov, causing the step to fail on subsequent runs. With this
change we will always install the latest version of this crate.

Author: Molter73

.github/workflows/ci.yml

@@ -88,7 +88,7 @@ jobs:
     - name: Install cargo-llvm-cov
       run: |
         rustup component add llvm-tools
-        cargo install cargo-llvm-cov
+        cargo install --force cargo-llvm-cov
 
     - name: Generate coverage
       run: make coverage