Add missing import statements

Author: cowtowncoder

avro/src/test/java/com/fasterxml/jackson/dataformat/avro/schema/SchemaGenerationTest.java

@@ -2,6 +2,8 @@
 
 import java.nio.ByteBuffer;
 import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.annotation.JsonAlias;
 import com.fasterxml.jackson.annotation.JsonProperty;