Consistently declare @⁠Nullable on parameter in equals() implementations

Closes gh-36075

Signed-off-by: 木葉 Scarlet <93977077+mukjepscarlet@users.noreply.github.com>

spring-test/src/main/java/org/springframework/test/context/bean/override/BeanOverrideContextCustomizer.java

@@ -18,6 +18,8 @@ package org.springframework.test.context.bean.override;
 
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.test.context.ContextCustomizer;
@@ -69,7 +71,7 @@ class BeanOverrideContextCustomizer implements ContextCustomizer {
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (other == this) {
 			return true;
 		}

spring-test/src/main/java/org/springframework/test/context/bean/override/BeanOverrideHandler.java

@@ -369,7 +369,7 @@ public abstract class BeanOverrideHandler {
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (other == this) {
 			return true;
 		}