Unstable items in rustdoc fail WCAG color contrast criterion

[GKFX]

https://doc.rust-lang.org/core/intrinsics/index.html has a long list of unstable functions. They have a text colour of #9a6e31, and due to the unstable class on their parent an opacity of 0.65. This results in text with too little contrast against their background to be read by all users.

Firefox can't use the opacity of parent elements to calculate colour contrast, but if I move the opacity into the text colour I calculate a ratio of 2.46:

This is much less than the recommended minimum value of 4.5 (WCAG 1.4.3). The little unsafe triangle is even fainter as it starts pale and is then also made 65% opaque. The contrast should be increased. This might be by removing the opacity rule and indicating instability by a symbol, or some other means.

It might be worth lumping this issue into #59845, but as it's quite specific I thought I'd file it as its own issue initially.