ci: note that we should install pkgconf in future

As pkg-config is now just redirected to the later, but changing this likely
depends on the GHA image being updated first.

.github/workflows/ci.yml

@@ -109,7 +109,8 @@ jobs:
         run: |
           # A workaround for "The `brew link` step did not complete successfully" error.
           brew install --quiet python@3 || brew link --overwrite python@3
-          brew install --quiet coreutils ninja pkg-config gnu-getopt ccache boost libevent zeromq qt@5 qrencode
+          # Update to install pkgconf, once the GHA image has been updated.
+          brew install --quiet coreutils ninja gnu-getopt ccache boost libevent zeromq qt@5 qrencode
 
       - name: Set Ccache directory
         run: echo "CCACHE_DIR=${RUNNER_TEMP}/ccache_dir" >> "$GITHUB_ENV"