Remove dependency management for Spring Shell

While the benign exception that Gemfire outputs is unfortunate, it
isn't sufficient justification for adding dependency management for
Spring Shell.

Closes gh-5444

spring-boot-samples/spring-boot-sample-data-gemfire/pom.xml

@@ -23,19 +23,11 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-data-gemfire</artifactId>
 		</dependency>
-
-		<dependency>
-			<groupId>org.springframework.shell</groupId>
-			<artifactId>spring-shell</artifactId>
-			<scope>runtime</scope>
-		</dependency>
-
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-configuration-processor</artifactId>
 			<optional>true</optional>
 		</dependency>
-
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-test</artifactId>