chore(spanner): Update CODEOWNERS (#3615)

Author: sakthivelmanii

.github/CODEOWNERS

@@ -5,8 +5,4 @@
 # https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-syntax
 
 # The @googleapis/api-spanner-java is the default owner for changes in this repo
-*                       @googleapis/yoshi-java @googleapis/api-spanner-java
-**/*.java               @googleapis/api-spanner-java
-
-# The java-samples-reviewers team is the default owner for samples changes
-samples/**/*.java       @googleapis/java-samples-reviewers @googleapis/api-spanner-java
+*                       @googleapis/yoshi-java @googleapis/spanner-client-libraries-java