bump gl-plot2d requirement

Author: etpinard

package.json

@@ -66,7 +66,7 @@
     "gl-line3d": "^1.1.0",
     "gl-mat4": "^1.1.2",
     "gl-mesh3d": "^1.2.0",
-    "gl-plot2d": "^1.1.8",
+    "gl-plot2d": "^1.1.9",
     "gl-plot3d": "^1.5.1",
     "gl-pointcloud2d": "^1.0.0",
     "gl-scatter2d": "^1.0.5",