meta-qt5: update layer

Update to Qt 5.12.2 (final)

Task-number: QTBUG-73533
Change-Id: I8924477ea6d381f823ba90344494d1ae121db078
Reviewed-by: Samuli Piippo <samuli.piippo@qt.io>

scripts/manifest.xml

@@ -26,7 +26,7 @@
            path="sources/meta-openembedded"/>
   <project name="meta-qt5"
            remote="qtyocto"
-           revision="439f7be65f681d4e45f30571082e38791cca2ef2"
+           revision="126927ef1b7077e7b82cd26b8d35f381cf3ff3a9"
            path="sources/meta-qt5"/>
   <project name="meta-mingw"
            remote="qtyocto"