Turn off the error message for requiring a certain version to use a custom step, let CI tell us how it goes.

Author: nedtwigg

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/FormatExtension.java

@@ -487,12 +487,6 @@ private void readObject(java.io.ObjectInputStream stream) throws java.io.IOExcep
 	 */
 	public void custom(String name, FormatterFunc formatter) {
 		requireNonNull(formatter, "formatter");
-		if (badSemverOfGradle() < badSemver(SpotlessPlugin.VER_GRADLE_minVersionForCustom)) {
-			throw new GradleException("The 'custom' method is only available if you are using Gradle "
-					+ SpotlessPlugin.VER_GRADLE_minVersionForCustom
-					+ " or newer, this is "
-					+ GradleVersion.current().getVersion());
-		}
 		addStep(FormatterStep.createLazy(name, () -> globalState, SerializedFunction.alwaysReturns(formatter)));
 	}