Remove unused test imports in jetty-nosql

[janbartel]

jetty-10

Unused test imports present in jetty-nosql:

    <dependency>
      <groupId>org.eclipse.jetty</groupId>
      <artifactId>jetty-slf4j-impl</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.eclipse.jetty.toolchain</groupId>
      <artifactId>jetty-test-helper</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.eclipse.jetty.tests</groupId>
      <artifactId>test-sessions-common</artifactId>
      <scope>test</scope>
    </dependency>