Use jruby artifact instead of jruby complete

[sschmittBt]

Using jruby-complete as dependency has some side effects, mainly that it is a shadow-jar and includes e.g. joda-time directly instead of as a dependency.
It would be better to use

<dependency>
    <groupId>org.jruby</groupId>
    <artifactId>jruby</artifactId>
    <version>9.1.7.0</version>
</dependency>

instead, to allow dependency resolution to manage the dependencies.