Out of date comment in TabletServerMetricsUtil

[DomGarguilo]

Describe the bug
TabletServerMetricsUtil javadoc mentions Hadoop metrics2 which we no longer use. This comment should be updated.

accumulo/server/tserver/src/main/java/org/apache/accumulo/tserver/metrics/TabletServerMetricsUtil.java

Lines 25 to 29 in e682a2f

	/**
	* Wrapper around extracting metrics from a TabletServer instance
	*
	* Necessary to support both old custom JMX metrics and Hadoop Metrics2
	*/

Versions (OS, Maven, Java, and others, as appropriate):

• Affected version(s) of this project: 2.1.2 and up

[DomGarguilo]

Did a quick search and found these mentions of hadoop metrics2 as well:

accumulo/core/src/main/java/org/apache/accumulo/core/conf/Property.java

Lines 386 to 387 in 6d0b476

	MANAGER_FATE_METRICS_ENABLED("manager.fate.metrics.enabled", "true", PropertyType.BOOLEAN,
	"Enable reporting of FATE metrics in JMX (and logging with Hadoop Metrics2).", "1.9.3"),

accumulo/core/src/main/java/org/apache/accumulo/core/conf/Property.java

Lines 928 to 929 in 6d0b476

	GC_METRICS_ENABLED("gc.metrics.enabled", "true", PropertyType.BOOLEAN,
	"Enable detailed gc metrics reporting with hadoop metrics.", "1.10.0"),

These could probably all be fixed in one PR

[EdColeman]

MANAGER_FATE_METRICS_ENABLED and MANAGER_FATE_METRICS_ENABLED Look like they are unused and have been marked deprecated. If so, maybe they can be removed?

[EdColeman]

Fixed by #4503