Remove duplicate image source providers (#4289)

Signed-off-by: Kudryavcev Nikolay <kydry.nikolau@gmail.com>

syft/get_source_config_test.go

@@ -0,0 +1,37 @@
+package syft
+
+import (
+	"testing"
+
+	"github.com/anchore/stereoscope"
+	"github.com/anchore/syft/syft/source/sourceproviders"
+)
+
+func TestGetProviders_DefaultImagePullSource(t *testing.T) {
+	userInput := ""
+	cfg := &GetSourceConfig{DefaultImagePullSource: stereoscope.RegistryTag}
+	allSourceProviders := sourceproviders.All(userInput, cfg.SourceProviderConfig)
+
+	providers, err := cfg.getProviders(userInput)
+	if err != nil {
+		t.Errorf("Expected no error for DefaultImagePullSource parameter, got: %v", err)
+	}
+
+	if len(providers) != len(allSourceProviders) {
+		t.Errorf("Expected %d providers, got %d", len(allSourceProviders), len(providers))
+	}
+}
+
+func TestGetProviders_Sources(t *testing.T) {
+	userInput := ""
+	cfg := &GetSourceConfig{Sources: []string{stereoscope.RegistryTag}}
+
+	providers, err := cfg.getProviders(userInput)
+	if err != nil {
+		t.Errorf("Expected no error for Sources parameter, got: %v", err)
+	}
+
+	if len(providers) != 1 {
+		t.Errorf("Expected 1 providers, got %d", len(providers))
+	}
+}