[JENKINS-58296] Revert "[JENKINS-53462] Submit form on Firefox as well" (#4246)

* [JENKINS-58296] Revert "[JENKINS-53462] Submit form on Firefox as well"

This reverts commit acc4eec6.
This change had been made in Jenkins to anticipate Firefox not dispatching
untrusted submit events anymore in v69, but this has actually been backed out.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1370630

Since this change seems to have introduced a double-submission bug on forms
with inputs of type "file", reverting sounds like the next logical step.

* [JENKINS-58296] added comment about the Firefox case

war/src/main/webapp/scripts/yui/button/button-debug.js

@@ -2717,9 +2717,18 @@ version: 2.9.0
                     WILL cause the form's "submit" event to fire, but WILL NOT 
                     submit the form.  Therefore, we need to call the "submit" 
                     method as well.
+                    In Firefox, dispatching a "submit" event still submits the form,
+                    so there is no need to call the "submit" method.
+                    This might change in the future though:
+                    https://bugzilla.mozilla.org/show_bug.cgi?id=1370630
+                    In the mean time, we should not make a redundant call to "submit",
+                    because it leads to the form being submitted twice in some cases:
+                    https://issues.jenkins-ci.org/browse/JENKINS-58296
+                    TODO: once we know the exact Firefox version which will change this
+                    behavior, we should add a "UA.gecko >= XX" condition and call "submit".
                 */
               
-                if ((UA.ie || UA.webkit || UA.gecko) && bSubmitForm) {
+                if ((UA.ie || UA.webkit) && bSubmitForm) {
         
                     oForm.submit();