preferences-window: Cancel search from keyboard

Fixes: Librem5/libhandy#206
11 jobs for my_work_fix_206 in 16 minutes and 33 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #253257
librem5
api-visibility

00:02:46

passed #253259
librem5
build-debian-clang

00:04:04

passed #253258
librem5
build-debian-gcc

00:03:06

passed #253260
librem5
build-fedora-gcc

00:03:54

 
  Test+Docs
passed #253261
librem5
build-gtkdoc

00:02:43

passed #253262
librem5
unit-test

00:02:40

42.3%
 
  Package
passed #253263
librem5
package-debian-buster

00:02:28

passed #253264
librem5:arm64
package-debian-buster:arm64

00:06:01

passed #253265
flatpak
package-flatpak

00:01:39

 
  Test Package
passed #253266
librem5
autopkgtest-debian-buster-package

00:03:27

passed #253267
librem5
lintian-debian-buster-package

00:01:12