Make the cursor a pointer for summaries

[wooster0]

I thought it might look nicer to make the cursor a pointer if the user hovers over summaries. I think it can help indicate to the user that this text is actually clickable, just like buttons.
Here's one example where I expect this to be effective (the "Advanced"):

I thought of also adding user-select: none; but buttons don't use it either so I didn't use it here.

Signed-off-by: r00ster91 <r00ster91@proton.me>

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Here's what your changelog entry will look like:

✨ Features

• Make the cursor a pointer for summaries (#8597). Contributed by @r00ster91.

[SimonBrandner]

LGTM codewise; this might need a design review - let me check