Fix build, remove TestModule.UTest from AmmInternalModule

[lefou]

This fixes the issue #1386:

> ./mill -i amm.repl[3.2.2].test
GITHUB REF None
fatal: no tag exactly matches 'cdeaa580bf128779686991a838623dd3a75af49b'
[296/296] amm.repl[3.2.2].test
java.lang.ClassNotFoundException: utest.runner.Framework
java.lang.ClassNotFoundException: utest.runner.Framework
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:476)
    at mill.api.ClassLoader$$anon$1.findClass(ClassLoader.scala:47)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:594)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:527)
    at mill.testrunner.TestRunner$.framework(TestRunner.scala:412)
    at mill.testrunner.TestRunner$.$anonfun$main$2(TestRunner.scala:252)
    at mill.testrunner.TestRunner$.$anonfun$runTestFramework$2(TestRunner.scala:326)
    at mill.util.Jvm$.inprocess(Jvm.scala:30)
    at mill.testrunner.TestRunner$.runTestFramework(TestRunner.scala:320)
    at mill.testrunner.TestRunner$.main(TestRunner.scala:258)
    at mill.testrunner.TestRunner.main(TestRunner.scala)
1 targets failed
amm.repl[3.2.2].test Test execution failed.

The issue is, that amm.repl[3.2.2] (defined by ReplModule which extends AmmModule which itself extends AmmoniteInternalModule) is itself a TestModule.UTest. That means, it already has a test target, so that the resolver will never search for a submodule that implements a defaultCommand.

After removing TestModule.UTest from AmmoniteInternalModule, the cli call properly resolves to amm.repl[3.2.2].test.test.

I'm curious to know, why this even compiled. We end up with two class members test, one def with the test target, and one object with the test sub-module.