Remove unnecessary code (#24610)

As title, remove unnecessary code.

modules/setting/config_provider.go

@@ -30,7 +30,6 @@ type ConfigProvider interface {
 	Section(section string) ConfigSection
 	NewSection(name string) (ConfigSection, error)
 	GetSection(name string) (ConfigSection, error)
-	DeleteSection(name string) error
 	Save() error
 }
 
@@ -40,12 +39,6 @@ type iniFileConfigProvider struct {
 	newFile bool // whether the file has not existed previously
 }
 
-// NewEmptyConfigProvider create a new empty config provider
-func NewEmptyConfigProvider() ConfigProvider {
-	cp, _ := NewConfigProviderFromData("")
-	return cp
-}
-
 // NewConfigProviderFromData this function is only for testing
 func NewConfigProviderFromData(configContent string) (ConfigProvider, error) {
 	var cfg *ini.File
@@ -121,11 +114,6 @@ func (p *iniFileConfigProvider) GetSection(name string) (ConfigSection, error) {
 	return p.File.GetSection(name)
 }
 
-func (p *iniFileConfigProvider) DeleteSection(name string) error {
-	p.File.DeleteSection(name)
-	return nil
-}
-
 // Save save the content into file
 func (p *iniFileConfigProvider) Save() error {
 	if p.opts.CustomConf == "" {