chore: Bump Chroma to v2.13.0, includes new Caddyfile lexer

[francislavoie]

https://github.com/alecthomas/chroma/releases/tag/v2.13.0

alecthomas/chroma#932

[francislavoie]

govulncheck complained about this:

Vulnerability #1: GO-2024-2605
    SQL injection in github.com/jackc/pgx/v4
  More info: https://pkg.go.dev/vuln/GO-2024-2605
  Module: github.com/jackc/pgx/v4
    Found in: github.com/jackc/pgx/v4@v4.18.0
    Fixed in: github.com/jackc/pgx/v4@v4.18.2
    Example traces found:
Error:       #1: modules/caddypki/acmeserver/acmeserver.go:269:26: acmeserver.openDatabase calls db.New, which eventually calls sanitize.SanitizeSQL

Required through smallstep:

$ go mod why github.com/jackc/pgx/v4
# github.com/jackc/pgx/v4
github.com/caddyserver/caddy/v2/modules/caddypki/acmeserver
github.com/smallstep/nosql
github.com/smallstep/nosql/postgresql
github.com/jackc/pgx/v4

So I ran this to bump the dep:

$ go get github.com/jackc/pgx/v4@v4.18.2