Change the overflow property from scroll to auto

[ProudBenzene]

📕 Description

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Fixes #253

What is the current behavior?

What is the new behavior?

Other Information or Things to be taken Note of

I got trouble with the same issue in #253 , and as far as I know, it seems that there was no successful reproduction on your end.

Here I made some debug about the phenomenon, and it seems that the overflow of the scrollbars of mathblocks is to blame.

When I set the property to scroll, the scrollbars would always be displayed, regardless of whether it contained an actual "bar"(like gif1) – and that's why the white stripes were formed; and when I set the property to auto, the scrollbar appeared only below long formulas(like gif2), instead of all the formulas like before. So the issue #253 was solved completely.

🔖 Type of change

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• [x] Bug fix (non-breaking change which fixes an issue)

✅ Checklist

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• [x] I followed the Developer's Guide when building for Primary

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• [x] My code follows the style guidelines of Primary
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings