move mime-mappings.properties to correct module

- there is a `FileNotFoundException` with the message `class path resource [org/springframework/boot/web/server/mime-mappings.properties] cannot be opened because it does not exist` if a static file is requested via url
- with spring boot 4.0.0 the modularization of the project was changed. in bb80db8 the web server auto-configure classes were moved into spring-boot-web-server module
- the `mime-mappings.properties` was still in the spring-boot module
- without java modules this is not an issue as spring-boot-web-server is part of the unnamed module and the property file can still be access
- however if a `requires spring.boot.web.server` is added the exception was thrown
- to fix this issue also move the property file to the new created module spring-boot-web-server

Signed-off-by: Stefan Würsten <[email protected]>

Author: stewue