bug#70383: Conf-mode[toml] badly set face property

[Alastair Irving]

When editting TOML files with conf-mode[toml] the face property is being 
set badly on certain characters.  This occurs in Emacs 29.3 (running 
with -q) but has been present in older versions. Steps to reproduce:

1. Create a file test.toml containing the following:


[package]
name = "test"
# See more keys and their definitions at 
https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]

2. Navigate to the d in dependencies and evaluate

(text-properties-at (point))

The output for me looks like

(face (font-lock-type-face font-lock-type-face font-lock-type-face 
font-lock-type-face font-lock-type-face font-lock-ty\
pe-face font-lock-type-face font-lock-type-face font-lock-type-face 
font-lock-type-face


It looks like something is wrong in the font-lock setup and the same 
face is being applied very many times.