fix(chloggen): improve error handling in DeleteEntries

[yoursanonymous]

Description

Previously, the DeleteEntries function in the chloggen tool would print deletion failures directly to stdout and return nil. This behavior bypassed the command's error-handling system, making it appear that the operation was successful even if it failed to clean up temporary entry files.

Changes:

• Refactored DeleteEntries in internal/chlog/entry.go to return an accumulated error using errors.Join.
• Removed fmt.Printf calls from the internal package to ensure errors are handled by the caller.
• This change ensures that the update command correctly reports failures if it cannot delete entry files after a successful changelog update.