golangci: remove deadcode/varcheck

Both linters are not supported anymore and trigger warnings every time
we try to lint our code.

To not see those warnings anymore, we remove them from the
configuration.

.golangci.yml

@@ -30,7 +30,6 @@ issues:
 linters:
   disable-all: true
   enable:
-    - deadcode
     - errcheck
     - goimports
     - gosimple
@@ -39,7 +38,6 @@ linters:
     - staticcheck
     - unconvert
     - unused
-    - varcheck
   fast: true
 
 # options for analysis running