Add missing whitespace.

Author: yuri-sergiichuk

datastore/src/main/java/io/spine/server/storage/datastore/DsRecordStorage.java

@@ -89,7 +89,7 @@ public static <I> Builder<I> newBuilder() {
     protected DsRecordStorage(
             RecordStorageBuilder<I,
                                  ? extends RecordStorage<I>,
-                                 ? extends RecordStorageBuilder<I,? extends RecordStorage<I>, ?>> b
+                                 ? extends RecordStorageBuilder<I, ? extends RecordStorage<I>, ?>> b
     ) {
         super(b.getEntityClass(), b.isMultitenant());
         this.typeUrl = TypeUrl.from(b.getDescriptor());