clean-up "nolint" comments, remove unused ones

- fix "nolint" comments to be in the correct format (`//nolint:<linters>[,<linter>`
  no leading space, required colon (`:`) and linters.
- remove "nolint" comments for errcheck, which is disabled in our config.
- remove "nolint" comments that were no longer needed (nolintlint).
- where known, add a comment describing why a "nolint" was applied.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/progress/escape.go

@@ -19,6 +19,6 @@ package progress
 const (
 	escape = "\x1b"
 	reset  = escape + "[0m"
-	red    = escape + "[31m" // nolint: deadcode, varcheck, unused
+	red    = escape + "[31m" //nolint:deadcode,unused,varcheck
 	green  = escape + "[32m"
 )