; Improve doc string of 'glyphless-char-display-control'

* lisp/international/characters.el
(glyphless-char-display-control): Doc fix.
10 jobs for master in 522 minutes and 26 seconds (queued for 29 seconds)
Status Job ID Name Coverage
  Build Images
passed #33993
build-image-inotify

02:21:09

 
  Normal
failed #33994
test-all-inotify

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  Platform Images
passed #33995
build-image-filenotify-gio

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passed #33996
build-image-gnustep

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  Platforms
failed #33997
test-filenotify-gio

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passed #33998
test-gnustep

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  Native Comp Images
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build-native-comp-speed0

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build-native-comp-speed1

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build-native-comp-speed2

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  Native Comp
failed #34002
test-native-comp-speed0

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Name Stage Failure
failed
test-native-comp-speed0 Native Comp
make: *** [check] Error 2
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
test-native-comp-speed0-6072370d
Uploading artifacts...
test-native-comp-speed0-6072370d/**/*.log: found 157 matching files
Uploading artifacts to coordinator... ok
id=34002 responseStatus=201 Created token=7SeuRUxa
ERROR: Job failed: exit code 2
failed
test-all-inotify Normal
make: *** [check-expensive] Error 2
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
test-all-inotify-6072370d
Uploading artifacts...
test-all-inotify-6072370d/**/*.log: found 157 matching files
Uploading artifacts to coordinator... ok
id=33994 responseStatus=201 Created token=3DgJWMKA
ERROR: Job failed: exit code 2
failed
test-filenotify-gio Platforms
make: Leaving directory '/checkout/test'
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
test-filenotify-gio-6072370d
Uploading artifacts...
test-filenotify-gio-6072370d/**/*.log: found 2 matching files
Uploading artifacts to coordinator... ok
id=33997 responseStatus=201 Created token=cDvuBxA8
ERROR: Job failed: exit code 2