Clean ReactorContextWebFilterTests imports

Issue: gh-4962

web/src/test/java/org/springframework/security/web/server/context/ReactorContextWebFilterTests.java

@@ -28,7 +28,6 @@ import org.springframework.security.core.context.ReactiveSecurityContextHolder;
 import org.springframework.security.core.context.SecurityContext;
 import org.springframework.security.core.context.SecurityContextImpl;
 import org.springframework.security.test.web.reactive.server.WebTestHandler;
-import org.springframework.test.context.TestPropertySource;
 import org.springframework.web.server.WebFilter;
 import org.springframework.web.server.WebFilterChain;
 import org.springframework.web.server.handler.DefaultWebFilterChain;