Use request.CTX instead of *request.Context (#24877)

* Use request.CTX instead of *request.Context

* Fix tests

server/channels/app/saml.go

@@ -23,7 +23,7 @@ const (
 	SamlIdpCertificateName    = "saml-idp.crt"
 )
 
-func (a *App) GetSamlMetadata(c *request.Context) (string, *model.AppError) {
+func (a *App) GetSamlMetadata(c request.CTX) (string, *model.AppError) {
 	if a.Saml() == nil {
 		err := model.NewAppError("GetSamlMetadata", "api.admin.saml.not_available.app_error", nil, "", http.StatusNotImplemented)
 		return "", err