Changed: Remove redundant cache restore keys for cargo-llvm-cov

Remove the broad restore-keys pattern to ensure only exact version matches
are used from the cache, preventing potential version mismatches during
CI runs.

Refs: #101

Author: acgetchell

.github/workflows/codecov.yml

@@ -41,8 +41,6 @@ jobs:
         with:
           path: ~/.cargo/bin/cargo-llvm-cov
           key: cargo-llvm-cov-${{ runner.os }}-${{ env.CARGO_LLVM_COV_VERSION }}
-          restore-keys: |
-            cargo-llvm-cov-${{ runner.os }}-
 
       - name: Install cargo-llvm-cov
         run: |