remove old com.yammer.metrics dependency

v2 of the metrics library (with the yammer namespace) is no longer used
by anything in Helios since Helios was upgraded to 0.7.1 of dropwizard
in 590780d.

helios-services/pom.xml

@@ -233,10 +233,6 @@
       <artifactId>raven-logback</artifactId>
       <version>4.1.1</version>
     </dependency>
-    <dependency>
-      <groupId>com.yammer.metrics</groupId>
-      <artifactId>metrics-core</artifactId>
-    </dependency>
     <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty</artifactId>

helios-system-tests/pom.xml

@@ -85,10 +85,6 @@
       <artifactId>raven-logback</artifactId>
       <version>4.1.1</version>
     </dependency>
-    <dependency>
-      <groupId>com.yammer.metrics</groupId>
-      <artifactId>metrics-core</artifactId>
-    </dependency>
     <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty</artifactId>

helios-system-tests/src/main/java/com/spotify/helios/system/LoggingTestWatcher.java

@@ -121,7 +121,6 @@ private void setupFileLogging(final String name) {
     configureLogger("org.eclipse.jetty", Level.ERROR);
     configureLogger("org.apache.curator", Level.ERROR);
     configureLogger("org.apache.zookeeper", Level.ERROR);
-    configureLogger("com.yammer.metrics", Level.ERROR);
     configureLogger("com.spotify.helios", Level.DEBUG);
   }
 

helios-testing-common/src/main/resources/logback-test.xml

@@ -46,9 +46,6 @@
   <logger name="org.eclipse.jetty" level="${externalLoggingLevel:-ERROR}">
     <appender-ref ref="EXTERNAL_STDERR"/>
   </logger>
-  <logger name="com.yammer.metrics" level="${externalLoggingLevel:-ERROR}">
-    <appender-ref ref="EXTERNAL_STDERR"/>
-  </logger>
 
   <logger name="com.spotify.helios" level="${heliosLoggingLevel:-DEBUG}"/>
 

pom.xml

@@ -240,11 +240,6 @@
           </exclusion>
         </exclusions>
       </dependency>
-      <dependency>
-        <groupId>com.yammer.metrics</groupId>
-        <artifactId>metrics-core</artifactId>
-        <version>2.2.0</version>
-      </dependency>
       <dependency>
         <groupId>com.google.code.findbugs</groupId>
         <artifactId>jsr305</artifactId>