Minor: make it easier to find fix instructions when cargo fmt on parquet fails (#6886)

* Minor: make it easier to find instructions when fmt fails

* purposely introduce a fmt issue

* Revert "purposely introduce a fmt issue"

This reverts commit 440e520.

* Update .github/workflows/rust.yml

Co-authored-by: Ed Seidl <etseidl@users.noreply.github.com>

---------

Co-authored-by: Ed Seidl <etseidl@users.noreply.github.com>

Author: alamb

.github/workflows/rust.yml

@@ -101,12 +101,13 @@ jobs:
       - name: Format arrow
         run: cargo fmt --all -- --check
       - name: Format parquet
-        # Many modules in parquet are skipped, so check parquet separately. If this check fails, run:
-        #   cargo fmt -p parquet -- --config skip_children=true `find ./parquet -name "*.rs" \! -name format.rs`
-        # from the top level arrow-rs directory and check in the result.
+        # Many modules in parquet are skipped, so check parquet separately
         # https://github.com/apache/arrow-rs/issues/6179
         working-directory: parquet
-        run: cargo fmt -p parquet -- --check --config skip_children=true `find . -name "*.rs" \! -name format.rs`
+        run: |
+          # if this fails, run this from the parquet directory:
+          # cargo fmt -p parquet -- --config skip_children=true `find . -name "*.rs" \! -name format.rs`
+          cargo fmt -p parquet -- --check --config skip_children=true `find . -name "*.rs" \! -name format.rs`
       - name: Format object_store
         working-directory: object_store
         run: cargo fmt --all -- --check