emscripten: Update deprecated calls to EM_ASM*.

`EM_ASM_` and `EM_ASM_INT_V` are calls that have been deprecated
for a long time.

Since the return value isn't used for the call to `EM_ASM_`, it
can be replaced with `EM_ASM`.

`EM_ASM_INT_V` is now (for the last few years) `EM_ASM_INT`.

(cherry picked from commit a8e89f2567b9069c919f9b21996e0a46cd4bb679)

src/audio/emscripten/SDL_emscriptenaudio.c

@@ -264,7 +264,7 @@ static int EMSCRIPTENAUDIO_OpenDevice(_THIS, const char *devname)
     this->hidden = (struct SDL_PrivateAudioData *)0x1;
 
     /* limit to native freq */
-    this->spec.freq = EM_ASM_INT_V({
+    this->spec.freq = EM_ASM_INT({
       var SDL2 = Module['SDL2'];
       return SDL2.audioContext.sampleRate;
     });

src/video/SDL_video.c

@@ -4565,7 +4565,7 @@ int SDL_ShowSimpleMessageBox(Uint32 flags, const char *title, const char *messag
     if (message == NULL) {
         message = "";
     }
-    EM_ASM_({
+    EM_ASM({
         alert(UTF8ToString($0) + "\n\n" + UTF8ToString($1));
     },
             title, message);