proxy-protocol possible values are not rendered correctly

[yahonda]

File: /master/tiproxy/tiproxy-configuration.md

https://docs.pingcap.com/tidb/dev/tiproxy-configuration#proxy-protocol shows the one of possible value is missing the closing backquote.

Possible values: `, v2`

The markdown itself looks correct https://github.com/pingcap/docs/blame/965c8767ee121c4bab722ee1e30a6c705481d8a5/tiproxy/tiproxy-configuration.md#L84

[kennytm]

No the markdown is not correct. Commonmark allows inline code blocks to be surrounded by N+1 backquotes in order to display N backquotes inside, e.g.

Quote identifiers (schema/table/column names) with the `` ` `` character like ``SELECT * FROM `x`.`y`;``.

Therefore using `` will not work for empty strings. (But separating it like ` ` is also incorrect as this seems to suggest that a space is a valid input to proxy-protocol.)

The tidb-server page uses "" for empty strings, but they will also use "v2" for consistency.