You can't remove those apps from firmware without root but you can uninstall any system app for current user or any user using ADB.
Assuming ADB is installed and PATH is set if not you can do it with a simple internet search.
Steps:
Obtain package name for app you want to remove.
Open Terminal/Command Prompt
Make sure device is connected by running adb devices -l
Run adb shell pm uninstall --user 0 <package name>
Done
Package Name
Facebook: com.facebook.katana
Messenger: com.facebook.orca
Proof of Concept
After some discussion in the comments I'm adding an example here that worked for me. I have uninstall Google Keyboard from my device for current user using command adb shell pm uninstall --user 0 com.google.android.inputmethod.latin

Before and after uninstalling (click images to enlarge)