As of gh-21783, Spring WebFlux uses a `TomcatHeadersAdapter`
implementation to directly address the native headers used by the
server.
In the case of Tomcat, "Content-Length" and "Content-Type" headers are
processed separately and should not be added to the native headers map.
This commit improves the `HandlerAdapter` implementation for Tomcat and
removes those headers, if previously set in the map. The adapter
already has a section that handles the Tomcat-specific calls for such
headers.
Fixes gh-24387
e1e8c165db