emscriptenaudio: Removed comment about Firefox not supporting userActivation.

It does now, and has since Firefox 120 (around November 2023).

src/audio/emscripten/SDL_emscriptenaudio.c

@@ -168,7 +168,7 @@ static bool EMSCRIPTENAUDIO_OpenDevice(SDL_AudioDevice *device)
                 SDL3.audioContext = new webkitAudioContext();
             }
             if (SDL3.audioContext) {
-                if ((typeof navigator.userActivation) === 'undefined') {  // Firefox doesn't have this (as of August 2023), use autoResumeAudioContext instead.
+                if ((typeof navigator.userActivation) === 'undefined') {
                     autoResumeAudioContext(SDL3.audioContext);
                 }
             }
@@ -284,7 +284,7 @@ static bool EMSCRIPTENAUDIO_OpenDevice(SDL_AudioDevice *device)
                 SDL3.audio_playback.silenceBuffer = SDL3.audioContext.createBuffer($0, $1, SDL3.audioContext.sampleRate);
                 SDL3.audio_playback.silenceBuffer.getChannelData(0).fill(0.0);
                 var silence_callback = function() {
-                    if ((typeof navigator.userActivation) !== 'undefined') {  // Almost everything modern except Firefox (as of August 2023)
+                    if ((typeof navigator.userActivation) !== 'undefined') {
                         if (navigator.userActivation.hasBeenActive) {
                             SDL3.audioContext.resume();
                         }