Do not set response status in ServerHttpObservationFilter

Prior to this commit, the `ServerHttpObservationFilter` would set the
response status (and possibly overwrite it) in case an exception is
found as an attribute.
While the exception itself should be used in the observation, the filter
should have no side effect on the response.

Fixes gh-29353

Author: bclozel

spring-web/src/main/java/org/springframework/web/filter/ServerHttpObservationFilter.java

@@ -27,7 +27,6 @@
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 
-import org.springframework.http.HttpStatus;
 import org.springframework.http.observation.DefaultServerRequestObservationConvention;
 import org.springframework.http.observation.ServerHttpObservationDocumentation;
 import org.springframework.http.observation.ServerRequestObservationContext;
@@ -117,7 +116,6 @@ protected void doFilterInternal(HttpServletRequest request, HttpServletResponse
 			if (!request.isAsyncStarted()) {
 				Throwable error = fetchException(request);
 				if (error != null) {
-					response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
 					observation.error(error);
 				}
 				observation.stop();

spring-web/src/test/java/org/springframework/web/filter/ServerHttpObservationFilterTests.java

@@ -70,7 +70,7 @@ void filterShouldUseThrownException() throws Exception {
 		ServerRequestObservationContext context = (ServerRequestObservationContext) this.request
 				.getAttribute(ServerHttpObservationFilter.CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE);
 		assertThat(context.getError()).isEqualTo(customError);
-		assertThatHttpObservation().hasLowCardinalityKeyValue("outcome", "SERVER_ERROR");
+		assertThatHttpObservation().hasLowCardinalityKeyValue("exception", "IllegalArgumentException");
 	}
 
 	@Test