fix: move prune channel from function literal to inline code

alpha/declcfg/diff.go

@@ -79,19 +79,6 @@ func (g *DiffGenerator) Run(oldModel, newModel model.Model) (model.Model, error)
 		return nil
 	}
 
-	// Prunes empty channels
-	pruneEmptyChannels := func() error {
-		for _, outputPkg := range outputModel {
-			for _, ch := range outputPkg.Channels {
-				if len(ch.Bundles) == 0 {
-					delete(outputPkg.Channels, ch.Name)
-				}
-
-			}
-		}
-		return nil
-	}
-
 	headsOnlyMode := len(oldModel) == 0
 	latestMode := !headsOnlyMode
 	isInclude := len(g.Includer.Packages) != 0
@@ -109,8 +96,13 @@ func (g *DiffGenerator) Run(oldModel, newModel model.Model) (model.Model, error)
 				return nil, err
 			}
 		} else {
-			if err := pruneEmptyChannels(); err != nil {
-				return nil, err
+			for _, outputPkg := range outputModel {
+				for _, ch := range outputPkg.Channels {
+					if len(ch.Bundles) == 0 {
+						delete(outputPkg.Channels, ch.Name)
+					}
+
+				}
 			}
 		}