ProjectExplorer: Simplify BuildStep::init() signature

The extra parameter was always computed but used only in one place,
and that use got removed lately.

Change-Id: Ie10c0107ca70ee97ce03f83294992aab8d1a3ffe
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/nim/project/nimcompilercleanstep.cpp

@@ -52,7 +52,7 @@ BuildStepConfigWidget *NimCompilerCleanStep::createConfigWidget()
     return new NimCompilerCleanStepConfigWidget(this);
 }
 
-bool NimCompilerCleanStep::init(QList<const BuildStep *> &)
+bool NimCompilerCleanStep::init()
 {
     FileName buildDir = buildConfiguration()->buildDirectory();
     bool result = buildDir.exists();