Missing quotes in a tooltip results in error while creating graph.

[Vrixyz]

Follow up on : https://github.com/Jondolf/avian/pull/383/files#r1768146223

Error message while running dot -Tsvg dump.dot:

Error: dump.dot: syntax error in line 129 near ':'

line 129:

"node_System(5)" -> "node_System(6)" ["lhead"="", "ltail"="", "tooltip"=<Plugin>build::{{closure}} → solve_constraint<FixedJoint, 2>, "color"="#3363bb"]

I can fix it manually by adding the quote for tooltip value.

I imagine this is an upstream bug from petgraph, but I'm letting breadcrumbs everywhere to have the most context.