fix: add required import for jdk8

Author: Nicola Di Falco

spring-shell-core/src/main/java/org/springframework/shell/component/NumberInput.java

@@ -30,6 +30,7 @@
 import org.springframework.shell.component.NumberInput.NumberInputContext;
 import org.springframework.shell.component.context.ComponentContext;
 import org.springframework.shell.component.support.AbstractTextComponent;
+import org.springframework.shell.component.support.AbstractTextComponent.TextComponentContext;
 import org.springframework.shell.component.support.AbstractTextComponent.TextComponentContext.MessageLevel;
 import org.springframework.util.NumberUtils;
 import org.springframework.util.StringUtils;