bump bevy_rapier2d for fixes implemented in v0.20.0

[odecay]

This fixes #227 from my testing. I think this https://github.com/dimforge/bevy_rapier/pull/250 addressed it and bumping version included this fix.

[odecay]

bors merge

[bors[bot]]

Build succeeded:

• Check Rust formatting
• Clippy correctness checks (wasm32-unknown-unknown, web-target)
• Clippy correctness checks (x86_64-unknown-linux-gnu, target)