Previously, if Actuator was being used in a non-web app such that
spring-web was not on the classpath, the app would fail to start
if Jackson 2 was present. This occured as the auto-configuration
for the EndpointJackson2ObjectMapper tried to use spring-web's
Jackson2ObjectMapperBuilder that was not present.
This commit updates the auto-configuration to back off when
Jackson2ObjectMapperBuilder is absent, aligning it with the
behavior of JacksonEndpointAutoConfiguration in 3.5.
Fixes gh-47788
Andy Wilkinson
Phillip Webb
Moritz Halbritter