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
 

libraries/stdlib/wasm/src/kotlin/JsInterop.kt

@@ -17,7 +17,6 @@ package kotlin
  *
  * This is a temporary annotation because K/Wasm <-> JS interop is not designed yet.
  */
-@Deprecated("@JsFun annotation is deprecated, use `fun f() = js(\"code\")` instead.")
 @Target(AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER)
 @Retention(AnnotationRetention.BINARY)
 public annotation class JsFun(val code: String)