Bug 1781434 - temporarily disable test_modal_prompts.html on win10_2004 r=intermittent-reviewers,jmaher DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D157361

toolkit/components/prompts/test/chrome.ini

@@ -4,6 +4,9 @@ support-files =
   chromeScript.js
 
 [test_modal_prompts.html]
-skip-if = toolkit == 'android' || (os == 'linux' && (debug || asan)) #android: TIMED_OUT (For Linux : 950636)
+skip-if = 
+  toolkit == 'android' 
+  os == 'linux' && (debug || asan) #android: TIMED_OUT (For Linux : 950636)
+  win10_2004 # Bug 1781434
 [test_modal_select.html]
-skip-if = toolkit == 'android' #android: TIMED_OUT
+skip-if = toolkit == 'android' #android: TIMED_OUT