fix(scheduler): clear buried questions on new day

[mparq]

the logic here seemed to be half-there but maybe missed in a refactor?
the method clearIfNewDay was already implemented but not used anywhere in the codebase. the method is now called and
questionPostponementList.write now sets buryDate to the current date when called.

[mparq]

I'm not sure, but maybe fixes #1175 and #1192 (possibly others). @st3v3nmw let me know if this looks right. I am new to the codebase and it is pretty complex but the change is hopefully isolated. I just tried to solve this because I had the issue where my flashcards would never show up for review. This fix seems to fix the problem I was seeing but the nature of the fix seems to suggest that this would be broken for everybody using the bury sibling cards option?

[st3v3nmw]

The fix overall makes sense but I'll update the function so that we can modify this.plugin.data directly instead of passing it.

P.S. I think we don't need the extra change in write since clearIfNewDay will already write data.buryDate.

[mparq]

Thanks @st3v3nmw! That makes sense. I actually don't remember why, but I was seeing that the buryDate was never changing from null without updating this.plugin.data in write... but now that I'm looking at the code again I can't figure out why that would be. Feel free to remove it, it could have just been something with how I was testing the change.