chore(ci): update location of code style document

Author: tottoto

.github/workflows/CI.yml

@@ -46,7 +46,7 @@ jobs:
       - name: cargo fmt --check
         run: |
           if ! rustfmt --check --edition 2021 $(git ls-files '*.rs'); then
-            printf "Please run \`rustfmt --edition 2021 \$(git ls-files '*.rs')\` to fix rustfmt errors.\nSee CONTRIBUTING.md for more details.\n" >&2
+            printf "Please run \`rustfmt --edition 2021 \$(git ls-files '*.rs')\` to fix rustfmt errors.\nSee docs/CODE_STYLE.md for more details.\n" >&2
             exit 1
           fi