ci: fix install-action SHA for cargo-llvm-cov

The previous SHA (8e6bcd...) was pinned to install-action's
'cargo-nextest' release tag, so the 'Install cargo-llvm-cov' step
was actually re-installing nextest and the subsequent coverage step
failed with 'cargo-llvm-cov not found'.

Pin instead to the SHA the 'cargo-llvm-cov' tag currently points to
(e5de28a).

Author: glima

.github/workflows/ci.yml

@@ -73,7 +73,7 @@ jobs:
         uses: extractions/setup-just@53165ef7e734c5c07cb06b3c8e7b647c5aa16db3 # v4.0.0
 
       - name: Install cargo-llvm-cov
-        uses: taiki-e/install-action@8e6bcdad38b75e3ed7b36872031a94f7c61006cc # cargo-llvm-cov
+        uses: taiki-e/install-action@e5de28abeb52d916c5e5875d54b21a9e738b61ec # cargo-llvm-cov
 
       - name: Generate LCOV coverage report
         run: just coverage-summary && cargo llvm-cov report --lcov --output-path lcov.info --ignore-filename-regex '/tests?/|/target/'