x/website: ref/mod: wrong character for grave accent

[rillig]

_content/ref/mod.md (https://golang.org/ref/mod) says:

grave accents (<code>&#60;</code>

which is rendered as:

grave accents (<

It should say instead:

grave accents (<code>&#x60;</code>

which is rendered as:

grave accents (`

[jerobado]

Hello, I'll send a PR shortly.

[gopherbot]

Change https://golang.org/cl/325989 mentions this issue: _content/ref: apply correct character for grave accent