android: remove checked in asset (#9426)

For sample-gltf-viewer, an asset was checked into the source tree.
But other assets are generated or copied from asset directories.

We remove the checked in gltf and copy the asset over during
build (as with other existing files).

android/samples/sample-gltf-viewer/build.gradle

@@ -17,12 +17,20 @@ filamentTools {
 }
 
 // don't forget to update MainACtivity.kt when/if changing this.
-tasks.register('copyMesh', Copy) {
+tasks.register('copyDamagedHelmetGltf', Copy) {
+    from file("../../../third_party/models/DamagedHelmet/DamagedHelmet.glb")
+    into file("src/main/assets/models")
+    rename {String fileName -> "helmet.glb"}
+}
+
+// don't forget to update MainACtivity.kt when/if changing this.
+tasks.register('copyBusterGltf', Copy) {
     from "../../../third_party/models/BusterDrone"
     into "src/main/assets/models"
 }
 
-preBuild.dependsOn copyMesh
+preBuild.dependsOn copyDamagedHelmetGltf
+preBuild.dependsOn copyBusterGltf
 
 clean.doFirst {
     delete "src/main/assets"