delete unused helper func

internal/cache/base.go

@@ -107,19 +107,6 @@ func destroyExpiredRenderers(now time.Time) {
 	})
 }
 
-// matchesACanvas returns true if the canvas represented by the canvasInfo object matches one of
-// the canvases passed in 'canvases', otherwise false is returned.
-func matchesACanvas(cinfo *canvasInfo, canvases []fyne.Canvas) bool {
-	canvas := cinfo.canvas
-
-	for _, obj := range canvases {
-		if obj == canvas {
-			return true
-		}
-	}
-	return false
-}
-
 type expiringCache struct {
 	expires time.Time
 }