Update verboseRequestMapping codemod to delete unused RequestMapping imports

[erosiec]

pixee:java/verbose-request-mapping replaces all uses of RequestMapping with shortcut variants, so unused RequestMapping imports can be deleted.

example: davewichers/TestGitHubAdvSec#7

In this case, two required imports were added:

+ import org.springframework.web.bind.annotation.GetMapping;
+ import org.springframework.web.bind.annotation.PostMapping;

so this import can be deleted:

import org.springframework.web.bind.annotation.RequestMapping;

Reported by: @davewichers

[Dave Wichers]

import org.springframework.web.bind.annotation.RequestMethod; can be removed too, as all uses of it were replaced as well.