Fix lower zorder traces behing some gridlines on overlayed suplots

[archmoj]

Supersedes #7149.

Here is a minimal code change compared to the rather complex solution proposed in #7149 and avoids several potential side effects catch by tests.

Fixes #7144 thanks to debugging sessions with @emilykl and @gvwilson

@plotly/plotly_js
@bpostlethwaite
@stephprobst
@my-tien

[archmoj]

@my-tien and @stephprobst Please use this bundle to test this within your system and let us know.

[archmoj]

@my-tien and @stephprobst Please use this bundle to test this within your system and let us know.

@stephprobst @my-tien were you able to test this bundle? https://output.circle-artifacts.com/output/job/07ec9652-70cc-4287-bfb0-c639ea6b2d39/artifacts/0/dist/plotly.min.js

[stephprobst]

@archmoj - I'm out of office and won't be able to test the package before the end of the week. Same for My-Tien.