chore: remove varcheck check (#849)

```
WARN [runner] The linter 'varcheck' is deprecated (since v1.49.0) due to: The owner seems to have abandoned the linter. Replaced by unused.
```

Signed-off-by: Rui Chen <[email protected]>

.golangci.yml

@@ -14,7 +14,7 @@ linters:
     - govet
     - ineffassign
     - typecheck
-    - varcheck
+    # - varcheck # deprecated - https://github.com/golangci/golangci-lint/issues/1841
     - stylecheck
     - tagliatelle
   disable: