Prior to this commit, the property was a Boolean with a null default.
If it was explicitly set by the user, a context customizer would use
that value to set it on the context. However, if it was not set, the default
wouldn't be tomcat's default but `false` because it was explicitly set to
`false` in `TomcatServletWebServerFactory`. This commit defaults the property
itself to `false` so that the default is more obvious to the user.

Fixes gh-20796