Remove maintenance badges from the Cargo.toml files. (#6286)

Several of these badges were out of date, with some crates in wide production
use marked as "experimental". Insted of trying to keep them up to date, just
remove them, since they are [no longer displayed on crates.io].

[no longer displayed on crates.io]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-badges-section

crates/runtime/Cargo.toml

@@ -50,9 +50,6 @@ once_cell = { workspace = true }
 [build-dependencies]
 cc = "1.0"
 
-[badges]
-maintenance = { status = "actively-developed" }
-
 [features]
 async = ["wasmtime-fiber"]