Update 'loop over paths in file' example (#872)

Replaced the cat-based approach with a direct input redirection method
using `while IFS= read -r`. This change ensures proper handling of the
last line which doesn't have a trailing new line.

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docs/batch-changes/batch-spec-cheat-sheet.mdx

@@ -31,10 +31,10 @@ on:
 
 steps:
   - run: |
-      cat /tmp/search-results | while read file;
+      while IFS= read -r file || [ -n "$file" ]
       do
         sed -i 's/OLD-VALUE/NEW-VALUE/g;' "${file}"
-      done
+      done < /tmp/search-results
     container: alpine:3
     files:
       /tmp/search-results: ${{ join repository.search_result_paths "\n" }}