Doc: Fix initialize() documentation

We do not share context between "processes", but between
"threads"

Change-Id: I20f558f913c1f19fc469ade6faab45762f42d528
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

src/webengine/api/qtwebengineglobal.cpp

@@ -59,7 +59,7 @@ namespace QtWebEngine {
 /*!
     \fn QtWebEngine::initialize()
 
-    Sets up an OpenGL Context that can be shared between processes. This has to be done after
+    Sets up an OpenGL Context that can be shared between threads. This has to be done after
     QGuiApplication is created, but before a Qt Quick window is created.
 
     This has the same effect as setting the Qt::AA_ShareOpenGLContexts