This reverts commit 7415ae6ec9.
The problems that caused me to write this commit in the first place have
been fixed. Using IDEA's test runner directly is nicer - e.g. for code
coverage integration.
IDEA's test runner doesn't work very well with multi-module projects,
particularly where there are different versions of jars in the
classpath.
Signed-off-by: Graham <gpe@openrs2.dev>