[ZEPPELIN-2373] Remove -Pyarn build profile

[AhyoungRyu]

What is this PR for?

Currently users who build Zeppelin from source need to include -Pyarn build profile to enable Yarn for embedded local Spark. This PR is to remove -Pyarn and make Yarn related libraries can be automatically downloaded without the profile during build time.

What type of PR is it?

just removed Yarn build profile in spark-dependencies/pom.xml

What is the Jira issue?

ZEPPELIN-2373

How should this be tested?

1. apply this patch and build Zeppelin with below command

mvn clean package -DskipTests -pl 'zeppelin-server, spark-dependencies, spark' --am

2. check spark-yarn_${scala.binary.version}.jar is downloaded(or included) during build time

[INFO] Including org.apache.spark:spark-yarn_2.10:jar:2.1.0 in the shaded jar.

In current master, the above line won't be shown if you don't use -Pyarn build profile. But with this patch, it will be shown without the profile.

Questions:

• Does the licenses files need update? no
• Is there breaking changes for older versions? no
• Does this needs documentation? no

[AhyoungRyu]

CI is green now.
@jongyoul Could you help me to review this PR?

[AhyoungRyu]

@felixcheung Thanks!
Merge into master if there are no more comments.