CI: unlock cargo-mutants build.

The locked version no longer compiles on nightly due to
<rust-lang/rust#99969>.

.github/workflows/ci.yml

@@ -148,7 +148,8 @@ jobs:
       # about caching the builds of them.
       # cargo-mutants is not used in this step but it will be cached for later use.
       run: |
-        cargo install --locked wasm-pack@0.12.1 cargo-about@0.6.1 cargo-mutants@24.1.0
+        cargo install --locked wasm-pack@0.12.1 cargo-about@0.6.1
+        cargo install cargo-mutants@24.5.0
 
 
     - run: df -h .
@@ -327,7 +328,7 @@ jobs:
 
       # Install cargo-mutants
       # This should usually be already installed, but is present in case of cache miss
-      - run: cargo install --locked cargo-mutants@24.1.0
+      - run: cargo install cargo-mutants@24.5.0
 
       - name: Relative diff
         run: |

.github/workflows/mutants.yml

@@ -22,7 +22,7 @@ jobs:
         run: rustup toolchain install stable --profile=minimal
 
       - name: Install cargo-mutants
-        run: cargo install --locked cargo-mutants@24.1.0
+        run: cargo install cargo-mutants@24.5.0
 
       - name: Run mutation testing for all-is-cubes
         timeout-minutes: 60