Makes Report Label use the actual node count

Before this change, the node count used in the label is the proposed amount
provided by the user. If some nodes were trimmed and the graph ended up with
less nodes than the user asked for, the report label will now reflect this.

internal/report/report.go

 func reportLabels(rpt *Report, g *graph.Graph, origCount, droppedNodes, droppedEdges int, fullHeaders bool) []string {
 	nodeFraction := rpt.options.NodeFraction
 	edgeFraction := rpt.options.EdgeFraction
-	nodeCount := rpt.options.NodeCount
+	nodeCount := len(g.Nodes)
 
 	var label []string
 	if len(rpt.options.ProfileLabels) > 0 {