Tests: Disable 3 tests that are flaky on CI

Tests/LibWeb/TestConfig.ini

@@ -312,3 +312,15 @@ Ref/input/wpt-import/css/css-contain/contain-paint-change-opacity.html
 
 ; Timing out; https://github.com/LadybirdBrowser/ladybird/issues/3912
 Text/input/wpt-import/html/rendering/replaced-elements/svg-inline-sizing/svg-inline.html
+
+; The number of subtests that pass is inconsistent, maybe a race condition?
+; https://github.com/LadybirdBrowser/ladybird/issues/4190
+Text/input/wpt-import/css/mediaqueries/media-query-matches-in-iframe.html
+
+; Inconsistently fails on CI.
+; https://github.com/LadybirdBrowser/ladybird/issues/4191
+Ref/input/scroll-iframe.html
+
+; Inconsistently times out because the echo server doesn't respond in time.
+; https://github.com/LadybirdBrowser/ladybird/issues/4192
+Text/input/WebSocket/echo.html