Remove redundant explicit imports (#1840)

src/main/java/com/zaxxer/hikari/metrics/dropwizard/CodahaleHealthChecker.java

@@ -18,8 +18,6 @@ package com.zaxxer.hikari.metrics.dropwizard;
 
 import java.sql.Connection;
 import java.sql.SQLException;
-import java.util.Properties;
-import java.util.SortedMap;
 import java.util.concurrent.TimeUnit;
 
 import com.codahale.metrics.MetricRegistry;

src/main/java/com/zaxxer/hikari/util/DriverDataSource.java

@@ -21,8 +21,6 @@ import java.sql.Driver;
 import java.sql.DriverManager;
 import java.sql.SQLException;
 import java.sql.SQLFeatureNotSupportedException;
-import java.util.Enumeration;
-import java.util.Map.Entry;
 import java.util.Properties;
 
 import javax.sql.DataSource;