Remove unnecessary manual setting of createKernelSpec task inputs

Gradle already knows that createKernelSpec depends on kernelspecfiles,
because they are part of the resources, so the task's classpath will
count as modified if the kernelspecfiles are modified.

build.gradle

@@ -69,7 +69,6 @@ processResources {
 
 mainClassName = "de.prob2.jupyter.Main"
 
-final KERNEL_SPEC_FILES_PATH = sourceSets.main.resources.sourceDirectories.singleFile.toPath().resolve(Paths.get("de", "prob2", "jupyter", "kernelspecfiles"))
 final KERNEL_SPEC_OUTPUT_PATH = project.buildDir.toPath().resolve(Paths.get("kernelspec"))
 
 task cleanKernelSpec(type: Delete) {
@@ -85,7 +84,6 @@ task createKernelSpec(type: JavaExec) {
 	if (project.hasProperty("probHome")) {
 		systemProperty("prob.home", project.probHome)
 	}
-	inputs.dir(KERNEL_SPEC_FILES_PATH.toFile())
 	outputs.dir(KERNEL_SPEC_OUTPUT_PATH.toFile())
 	doFirst {
 		mkdir(KERNEL_SPEC_OUTPUT_PATH)