bug#56393: Actually fix the long lines display bug

[Eli Zaretskii]

> Date: Sat, 09 Jul 2022 11:38:17 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: gerd.moellmann@gmail.com, larsi@gnus.org, 56393@debbugs.gnu.org
> 
> Then here's another recipe with long lines detection enabled:
> 
> emacs -Q
> C-x C-f src/xdisp.c RET
> C-n
> C-x i .../dictionary.json RET
> M->
> C-u 37100 C-p

Where can I get a one-line dictionary.json file?  I don't think I have
it here.