package/qt5x11extras: update hash source URL

Be more specific for the hash source URL and change from
summary page (.mirrorlist) to direct sha256 download page
(.sha256).

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qt5/qt5x11extras/5.12.7/qt5x11extras.hash

@@ -1,4 +1,4 @@
-# Hash from: https://download.qt.io/official_releases/qt/5.12/5.12.7/submodules/qtx11extras-everywhere-src-5.12.7.tar.xz.mirrorlist
+# Hash from: https://download.qt.io/official_releases/qt/5.12/5.12.7/submodules/qtx11extras-everywhere-src-5.12.7.tar.xz.sha256
 sha256 23895f4b1e84f3783526b9e17680df38c587601d4dfa6ff1b81ace432c480b96 qtx11extras-everywhere-src-5.12.7.tar.xz
 
 # Hashes for license files: