configure.ac: Bump inputproto dep to 2.3.99.1

This should have been part of 6cbcbc81525b131b5b94409ea870af663d5c28bb.

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
5 jobs for bump-inputproto in 3 minutes and 55 seconds (queued for 1 second)
Status Name Job ID Coverage
  Docker Image
passed debian-buster #10939608

00:00:24

 
  Build And Test
passed autotools #10939609

00:03:31

passed meson #10939610

00:02:20

passed meson-noglamor #10939611

00:01:55

passed mingw-cross-build #10939612

00:00:43