Extinction sessions report rewards but none was delivered

**Describe the bug**
This is more of a bug in the experiment itself than in the code, but the fix needs to be addressed in code. For context - in the learning mFISH experiments, we have 2 "extinction" sessions at the end of the training procedure where the water delivery is turned off but the lick spout remains in place so the mouse can report when it thinks it sees a change, but no reward will be delivered. However, the lack of reward delivery is not something specified by the camstim code, its determined by the operator physically turning the water off. so the camstim code is still logging that it attempted to deliver a reward, even though we know none was delivered. the behavior NWB files need to reflect this reality and should not report any rewards delivered in extinction sessions. we have been using the session_type OPHYS_6_images_B to indicate extinction sessions where water has been turned off, so i think the fix would be to add something to the code that accounts for this when creating the trials / events tables for this session type that manually sets the reward volume to 0 for all trials these sessions, and/or removes any false reward events from the table.

**To Reproduce**
Load a behavior NWB file for OPHYS_6_images_B (like this asset: f81382b4-d304-46ad-9524-6e8b900b2d3f) and look at trials and events tables - you will see instances of reward events and trials / licks where reward volume is not zero.

**Expected behavior**
OPHYS_6_images_B sessions should not have any reward events

**Screenshots**
I detected this when doing an assessment of reward rate across sessions and found that reward rate for OPHYS_6 sessions was not zero: