Remove FeatureFlags#EXAMPLE

[AB-xdev]

FeatureFlags#EXAMPLE states:

Example feature. Will be removed once the first real feature flag is added

It should therefore be removed

flow/flow-server/src/main/java/com/vaadin/experimental/FeatureFlags.java

Lines 60 to 64 in ec83c9f

	public static final Feature EXAMPLE = new Feature(
	"Example feature. Will be removed once the first real feature flag is added",
	"exampleFeatureFlag", "https://github.com/vaadin/flow/pull/12004",
	false,
	"com.vaadin.flow.server.frontend.NodeTestComponents$ExampleExperimentalComponent");