Fix output file list to use spaces instead of commas

[goruha]

what

• Change the file output variable separator from commas to spaces (${files// /,} → ${files// / })

why

• The previous substitution replaced spaces with commas, which produced an incorrect file pattern for downstream steps (e.g. git-auto-commit-action's file_pattern expects space-separated paths)
• This was a no-op substitution bug — the intent was to preserve space-separated file paths, not convert them to comma-separated

references

• Downstream usage in stefanzweifel/git-auto-commit-action file_pattern input

[github-actions]

These changes were released in v3.1.0.