Drop requirement for root tag to be named

Sponge does not name the root tag, this allows us to almost load their
schematics (except for a bug
https://github.com/SpongePowered/SpongeCommon/pull/3085)

worldedit-core/src/main/java/com/sk89q/worldedit/extent/clipboard/io/SpongeSchematicReader.java

@@ -149,9 +149,6 @@ public OptionalInt getDataVersion() {
 
     private CompoundTag getBaseTag() throws IOException {
         NamedTag rootTag = inputStream.readNamedTag();
-        if (!rootTag.getName().equals("Schematic")) {
-            throw new IOException("Tag 'Schematic' does not exist or is not first");
-        }
         CompoundTag schematicTag = (CompoundTag) rootTag.getTag();
 
         // Check