Always backup the original key first (just in case)!
# cp www.key www.key.orig
Then unencrypt the key with openssl. You’ll need the passphrase for the decryption process:
# openssl rsa -in www.key -out new.key
Now copy the new.key to the www.key file and you’re done. Next time you restart the web server, it should not prompt you for the passphrase.
This is useful in cases that you use private key with password in apache ssl configuration.