HADOOP-14138. Remove S3A ref from META-INF service discovery, rely on existing core-default entry.

Contributed by Steve Loughran

hadoop-tools/hadoop-aws/src/main/resources/META-INF/services/org.apache.hadoop.fs.FileSystem

@@ -15,4 +15,3 @@
 
 org.apache.hadoop.fs.s3.S3FileSystem
 org.apache.hadoop.fs.s3native.NativeS3FileSystem
-org.apache.hadoop.fs.s3a.S3AFileSystem