[WPE] Update Cog version for the WebKit build

https://bugs.webkit.org/show_bug.cgi?id=266351

Reviewed by Philippe Normand and Michael Catanzaro.

This updates Cog for the WPE build to the last one
(0~0.19.1-1-g843f874)

This fixes an issue with the DRM plugin for the RPi4
that causes Cog to not output anything on the screen.

Cog now depends on libportal, that dependency was added
to the Flatpak SDK in 272033@main

* Tools/PlatformWPE.cmake:

Canonical link: https://commits.webkit.org/272046@main

Tools/PlatformWPE.cmake

@@ -30,7 +30,7 @@ if (ENABLE_COG)
         set(WPE_COG_REPO "https://github.com/Igalia/cog.git")
     endif ()
     if ("${WPE_COG_TAG}" STREQUAL "")
-        set(WPE_COG_TAG "9e2dc0a086336d7cd025e50461d126992734672d")
+        set(WPE_COG_TAG "843f874484d09b9e492683a50f4707e584e3fcb6")
     endif ()
     # TODO Use GIT_REMOTE_UPDATE_STRATEGY with 3.18 to allow switching between
     # conflicting branches without having to delete the repo