Fix build after Spring Framework deprecation

See spring-projects/spring-framework#28905

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootContextLoader.java

@@ -244,12 +244,6 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 		return AnnotationConfigContextLoaderUtils.detectDefaultConfigurationClasses(declaringClass);
 	}
 
-	@Override
-	public ApplicationContext loadContext(String... locations) throws Exception {
-		throw new UnsupportedOperationException(
-				"SpringApplicationContextLoader does not support the loadContext(String...) method");
-	}
-
 	@Override
 	protected String[] getResourceSuffixes() {
 		return new String[] { "-context.xml", "Context.groovy" };

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/support/ErrorPageFilterIntegrationTests.java

@@ -186,11 +186,6 @@ class ErrorPageFilterIntegrationTests {
 			return context;
 		}
 
-		@Override
-		public ApplicationContext loadContext(String... locations) {
-			throw new UnsupportedOperationException();
-		}
-
 		@Override
 		protected String[] getResourceSuffixes() {
 			return EMPTY_RESOURCE_SUFFIXES;