chore: refactor linter configurations and settings

- Remove `deadcode` and `depguard` linters
- Remove `structcheck` linter
- Remove `varcheck` linter
- Remove `linters-settings` section

Signed-off-by: appleboy <[email protected]>

Author: appleboy

.golangci.yml

@@ -4,8 +4,6 @@ linters:
   fast: false
   enable:
     - bodyclose
-    - deadcode
-    - depguard
     - dogsled
     - dupl
     - errcheck
@@ -29,20 +27,12 @@ linters:
     - nolintlint
     - rowserrcheck
     - staticcheck
-    - structcheck
     - stylecheck
     - typecheck
     - unconvert
     - unparam
     - unused
-    - varcheck
     - whitespace
     - gofumpt
-
 run:
   timeout: 3m
-
-linters-settings:
-  dupl:
-    # tokens count to trigger issue, 150 by default
-    threshold: 200