Web: Fix a possible JS error.

Public issue https://github.com/mackron/miniaudio/issues/810

miniaudio.h

@@ -40454,6 +40454,10 @@ static ma_result ma_context_uninit__webaudio(ma_context* pContext)
     /* Remove the global miniaudio object from window if there are no more references to it. */
     EM_ASM({
         if (typeof(window.miniaudio) !== 'undefined') {
+            miniaudio.unlock_event_types.map(function(event_type) {
+                document.removeEventListener(event_type, miniaudio.unlock, true);
+            });
+
             window.miniaudio.referenceCount -= 1;
             if (window.miniaudio.referenceCount === 0) {
                 delete window.miniaudio;