[BUG] Horizontal line overlaps code formatting

[Piggered]

Describe the bug
A horizontal line followed by code formatted using an indentation of 4 spaces causes the horizontal line to overlap on the first line of the code.

To Reproduce
Steps to reproduce the behavior:

1. Submit a selftext post or comment with a horizontal line (---), followed by code formatted using the four-space indentation markdown.
   Example post

Expected behavior
The formatted code should display under the horizontal line.

Screenshots

Smartphone (please complete the following information):

• Device: Samsung Galaxy S9
• OS: Android 10
• Browser: N/A (Firefox)
• Version: 22.3.6 (and 20.0.3)

Additional context
N/A

[laurencedawson]

Fixed for the next release.