bug#62108: 30.0.50; icomplete-show-matches-on-no-input and icomplete breaks auto-insert in .el files

[Spencer Baugh]

1. Eval:
(setq icomplete-show-matches-on-no-input t)
(icomplete-mode t)
2. Open a .el file
3. M-x auto-insert
4. At the point where you're prompted for keywords, it's not possible to
   exit other than by C-g, so the skeleton is aborted halfway through.

fido-mode turns this variable on as well, but it has a binding for
icomplete-fido-exit which allows a fido-mode user to exit the keyword
prompt.

Perhaps a binding for a similar command should be added to regular
icomplete-mode?  Perhaps the very same binding?

At least, this class of hazards should be described in the docstring for
icomplete-show-matches-on-no-input.

Alternatively, perhaps the .el skeleton should be updated to work
differently.


In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.22.30, cairo version 1.15.12) of 2023-02-27 built on igm-qws-u22796a
Repository revision: af94369f90a5d3ad44dcc80d205665ccb2d41995
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: CentOS Linux 7 (Core)

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Memory information:
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