Revert "[Wasm] Deprecate @JsFun with warning"

Reason: Design of js(code) replacement is still in flux.
        It would be better to delay deprecation until we converge
        to proper solution.

This reverts commit 3566d918d2.

compiler/testData/diagnostics/wasmTests/jsInterop/jsFun.kt

@@ -1,5 +1,3 @@
-@file:Suppress("DEPRECATION")
-
 @JsFun("() => {}")
 external fun topLevelExternalFun(): Unit