bug#60834: configuration->documentation generates garbage @-command on fields beginning with numeric characters

[Bruno Victal <mirai@makinata.eu>]

Minimal example (with Guix REPL):

--8<---------------cut here---------------start------------->8---
scheme@(guix-user)> ,use (gnu services configuration)
scheme@(guix-user)> (define serialize-boolean (lambda (x y) #t))
scheme@(guix-user)> (define-configuration example-configuration (1-foo (boolean #t) "lorem ipsum"))
scheme@(guix-user)> (configuration->documentation 'example-configuration)
%example-configuration
@c %start of fragment

@deftp {Data Type} example-configuration
Available @code{example-configuration} fields are:

@table @asis
@item @code{#@{1-foo@}#} (default: @code{#t}) (type: boolean)
lorem ipsum

@end table

@end deftp


@c %end of fragment
scheme@(guix-user)> 
--8<---------------cut here---------------end--------------->8---