I tried this, but El Capitan has locked those files down hard.
That is the System Integrity Protection (SIP) kicking in, a new security feature in El Capitan.
You could disable it temporarily to be able to remove the installed camera raw bundle. The Genius Bar could help with that, if you are not confident about tempering with the system.
El Capitan is preventing even administrators from installing in the System directory, so you cannot accidentally download and install malware.
Yo could either disable the system Integrity protection temporarily and enable it again when done, or do the full monty and revert to your previous system version by restoring the system from a Time Machine backup: https://support.apple.com/kb/PH21950?viewlocale=en_US&locale=en_US
To disable SIP to be able to remove the installed RAW bundle you could try the following: (from a post by Yax Attax)
1. Restart computer holding down Command-R to boot up in Recovery Mode.
2. Go to menu bar and launch Terminal application.
3. At the command line prompt, type "csrutil disable" (without quotes), followed by the RETURN key.
4. Restart your computer, log in normally, remove the RAW support files and reinstall the older RAW support.
5. After you finish making your changes, restart into Recovery Mode a second time, launch Terminal from the menu bar again, and type "csrutil enable" (without quotes) followed by RETURN key to re-enable System Integrity protection.
6. Reboot a final time and log in normally.