change lockPref() to pref() in the .cfg

lockpref() prevents users from changing values in about:config but it also makes it very annoying in overrides as it requires to unlock a pref and the set its value. pref() doesn't prevent changes but instead it resets the value with each session, which is kind of a similar end result (eg. we don't want users to permanently flip a certain pref because it's bad for security) but less limiting and easier to override.

while locking makes sense in some cases (eg. internal prefs used for remapping UI links), it doesn't in many others and it gets in the way of user changes, so we could consider switching at least in some cases.