Drop redundant Assertions.assertThat static import in spring-webflux tests

OpenTelemetryAssertions extends Assertions, so AssertJ's assertThat
overloads are already in scope via the OpenTelemetryAssertions.assertThat
static import.

Author: trask

instrumentation/spring/spring-webflux/spring-webflux-5.0/testing/src/main/java/io/opentelemetry/instrumentation/spring/webflux/server/AbstractSpringWebFluxServerTest.java

@@ -13,7 +13,6 @@
 import static io.opentelemetry.semconv.ExceptionAttributes.EXCEPTION_STACKTRACE;
 import static io.opentelemetry.semconv.ExceptionAttributes.EXCEPTION_TYPE;
 import static java.util.stream.Collectors.toList;
-import static org.assertj.core.api.Assertions.assertThat;
 
 import io.opentelemetry.api.logs.Severity;
 import io.opentelemetry.instrumentation.testing.junit.InstrumentationExtension;

instrumentation/spring/spring-webflux/spring-webflux-5.0/testing/src/main/java/io/opentelemetry/instrumentation/spring/webflux/server/AbstractSpringWebfluxTest.java

@@ -30,7 +30,6 @@
 import static io.opentelemetry.semconv.UrlAttributes.URL_SCHEME;
 import static io.opentelemetry.semconv.UserAgentAttributes.USER_AGENT_ORIGINAL;
 import static java.util.stream.Collectors.toList;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Named.named;
 
 import io.opentelemetry.api.logs.Severity;