doc: repl deprecation styling results in unreadable text

[mscdex]

• Version: v7.x
• Platform: n/a
• Subsystem: doc

The styling of backtick blocks in deprecation messages was changed at some point for v7.x docs, causing this deprecation to be white on gray on red, making the text unreadable.

[Fishrock123]

This is probably due to f1a3755#diff-fa6d04f9f0d2df5a1320c28106ea0a32L356

Deprecation blocks should probably override it separately (per color?).