style: Use tabular font for clocks

So that the text has same size allocated and thus the text won't move
when the value changes, which is very much visible when clock shows
seconds
11 jobs for use-tabular-clock-font in 36 minutes and 21 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #344726
librem5
build:cross-debian-bullseye:i386

00:12:26

passed #344727
librem5
build:native-alpinelinux-edge

00:08:12

passed #344725
librem5
build:native-debian-bullseye

00:11:54

 
  Test+Docs
passed #344729
librem5
build-gtkdoc

00:04:09

passed #344731
librem5
check-license-headers

00:02:13

passed #344730
librem5
check-po

00:00:26

passed #344733
librem5
test:smoke:one-output

00:01:28

passed #344734
librem5
test:smoke:two-outputs

00:01:22

passed #344732
librem5
unit-test:native-alpinelinux-edge

00:00:40

passed #344728
librem5
unit-test:native-debian-bullseye

00:03:25

14.3%
 
  Package
passed #344735
librem5:arm64
package:deb-debian-bullseye:arm64

00:18:28