Update dependencies on '6.4.0' in qt/qtlanguageserver

Change-Id: Iad517f568f56d9ffe87cfa27211cc520cd5d9c82
Reviewed-by: Qt Submodule Update Bot <qt_submodule_update_bot@qt-project.org>

dependencies.yaml

 dependencies:
   ../qtbase:
-    ref: fb12a7f9b9a0c2d42ef47f4ff7dabcef9a58cd3d
+    ref: bc7e63385522c2020168cf367a8b3b1e6c6bc65e
     required: true