Don't export `__wasm_init_memory` on WebAssembly.
Since #72889, the Rust wasm target doesn't use --passive-segments, so remove the `--export=__wasm_init_memory`.
As documented in the [tool-conventions Linking convention], `__wasm_init_memory` is not intended to be exported.
[tool-conventions Linking convention]: 7c064f3048/Linking.md (shared-memory-and-passive-segments)