ci: remove unused depguard check for qtls (#4291)

Fortunately, qtls is a thing of the past.

.golangci.yml

@@ -2,16 +2,6 @@ run:
  skip-files:
  - internal/handshake/cipher_suite.go
 linters-settings:
- depguard:
- rules:
- qtls:
- list-mode: lax
- files:
- - "!internal/qtls/**"
- - "$all"
- deny:
- - pkg: github.com/quic-go/qtls-go1-20
- desc: "importing qtls only allowed in internal/qtls"
  misspell:
  ignore-words:
  - ect
@@ -20,7 +10,6 @@ linters:
  disable-all: true
  enable:
  - asciicheck
- - depguard
  - exhaustive
  - exportloopref
  - goimports