Fix variable name for main PR author check

Author: ludamad

scripts/merge-train/squash-pr.sh

@@ -62,7 +62,7 @@ authors_info=$(git log "$merge_base..$original_head" --no-merges --format='%an <
 co_authors=""
 while IFS= read -r author_line; do
   # Skip empty lines, the main PR author, AztecBot, and tech@aztecprotocol.com
-  if [[ -n "$author_line" ]] && [[ "$author_line" != *"$author_name"* ]] && [[ "$author_line" != *"$author_email"* ]] && [[ "$author_line" != *"AztecBot"* ]] && [[ "$author_line" != *"tech@aztecprotocol.com"* ]]; then
+  if [[ -n "$author_line" ]] && [[ "$author_line" != *"$pr_author"* ]] && [[ "$author_line" != *"$author_email"* ]] && [[ "$author_line" != *"AztecBot"* ]] && [[ "$author_line" != *"tech@aztecprotocol.com"* ]]; then
     co_authors="${co_authors}Co-authored-by: ${author_line}
 "
   fi