fix(collections): 🐛 collection improvements, ajustes no texto

Author: rcmoutinho

book/08-java-collections/sections/05-collection-improvements.asc

@@ -72,6 +72,7 @@ Map antes do computeIfPresent: {A=65, B=66}
 Map depois do computeIfPresent: {A=4225, B=4356}
 ----
 
+.Referências
 ****
 
 * Using Streams
@@ -80,4 +81,4 @@ Boyarsky, Jeanne; Selikoff, Scott. OCP: Oracle Certified Professional Java SE 8
 
 * https://www.baeldung.com/java-8-streams[The Java 8 Stream API Tutorial.]
 
-****
+****