Remove redundant len check around loop (#27464)

This pull request is a minor code cleanup.

From the Go specification (https://go.dev/ref/spec#For_range):

> "1. For a nil slice, the number of iterations is 0."
> "3. If the map is nil, the number of iterations is 0."

`len` returns 0 if the slice or map is nil
(https://pkg.go.dev/builtin#len). Therefore, checking `len(v) > 0`
before a loop is unnecessary.

---

At the time of writing this pull request, there wasn't a lint rule that
catches these issues. The closest I could find is
https://staticcheck.dev/docs/checks/#S103

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

modules/setting/config_provider.go

@@ -213,11 +213,9 @@ func NewConfigProviderFromFile(file string, extraConfigs ...string) (ConfigProvi
 		}
 	}
 
-	if len(extraConfigs) > 0 {
-		for _, s := range extraConfigs {
-			if err := cfg.Append([]byte(s)); err != nil {
-				return nil, fmt.Errorf("unable to append more config: %v", err)
-			}
+	for _, s := range extraConfigs {
+		if err := cfg.Append([]byte(s)); err != nil {
+			return nil, fmt.Errorf("unable to append more config: %v", err)
 		}
 	}