chore: drop instant on wasm

[timvw]

Summary

• bump reqwest-retry to 0.7.1 for a patch release slot
• update the wasm retry timer to wasmtimer 0.4.3 so the instant crate disappears from the dependency graph
• document the change in the changelog and link the advisory

Testing

• cargo test -p reqwest-retry
• cargo check -p reqwest-retry --target wasm32-unknown-unknown

Fixes #245
Refs genai-rs/langfuse-ergonomic#70

[timvw]

Rebased onto latest upstream/main and force-pushed. Waiting on the fresh CI run to go green.