x/pkgsite: three backticks are turned into a quotation mark followed by a single backtick even in indented block

[SamWhited]

When entering two backticks pkg.go.dev renders it as a quotation mark, like LaTeX. However, this also happens when three backticks are used in an indented block where I would expect the original text to remain unchanged, for example, in this pre-formatted block demonstrating a markdown like language: