[unity] Minor: increased package version after merge.

spine-unity/Assets/Spine/package.json

@@ -2,7 +2,7 @@
 	"name": "com.esotericsoftware.spine.spine-unity",
 	"displayName": "spine-unity Runtime",
 	"description": "This plugin provides the spine-unity runtime core.",
-	"version": "4.2.57",
+	"version": "4.2.58",
 	"unity": "2018.3",
 	"author": {
 		"name": "Esoteric Software",