[PP-1] Consider deprecating heading_id property from pagination templates

Add Stable9 issue since it is also a dependency.
General core issue has been merged.
Stable9 issue is RTBC.

This issue is already postponed, but the reason for postponement has changed.

This issue was filed as a follow-up to 🐛 Pager h4 causes accessibility flag on many pages Fixed .

Since then, I've made a very strong objection to removing the heading from the pagination template. In which case, the heading ID is still needed.

That would make this issue would a wont-fix. I'll leave it in a postponed state while the other is still being discussed.

I agree this is won't fix even if we make the heading configurable since we would still need the heading_id.

I'll still leave this open until those are resolved.

The solution bypasses the need for this so I'll close this.