Make PropertySourcesPlaceholderConfigurerTests pass on JDK 17

This change is required in Eclipse IDE but not for the Gradle build.

See gh-27947

spring-context/src/test/java/org/springframework/context/support/PropertySourcesPlaceholderConfigurerTests.java

@@ -445,7 +445,7 @@ public void setName(Optional<String> name) {
 		}
 	}
 
-	@Configuration
+	@Configuration(proxyBeanMethods = false)
 	static class IgnoreUnresolvablePlaceholdersFalseConfig {
 
 		@Value("${my.key}")
@@ -457,7 +457,7 @@ static PropertySourcesPlaceholderConfigurer pspc() {
 		}
 	}
 
-	@Configuration
+	@Configuration(proxyBeanMethods = false)
 	static class IgnoreUnresolvablePlaceholdersTrueConfig {
 
 		@Value("${my.key}")