[Glitch] Fix Cmd/Ctrl + Enter in the composer triggering confirmation dialog action

Port 6e294828d6 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/features/compose/components/compose_form.jsx

@@ -110,10 +110,12 @@ class ComposeForm extends ImmutablePureComponent {
   handleKeyDownPost = (e) => {
     if (e.key.toLowerCase() === 'enter' && (e.ctrlKey || e.metaKey)) {
       this.handleSubmit(e);
+      e.preventDefault();
     }
 
     if (e.key.toLowerCase() === 'enter' && e.altKey) {
       this.handleSecondarySubmit(e);
+      e.preventDefault();
     }
 
     this.blurOnEscape(e);